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Leif Azzopardi

Publication record assembled from the DBLP archive of ranked conferences.

Papers indexed

160

Venues

15

Active years

2003–2026

Best venue rank

A*

Where they publish

Papers

160 indexed papers, newest first.

YearVenueTitleAuthors
2026CHIIRInformation Farming: From Berry Picking to Berry Growing.Leif Azzopardi, Adam Roegiest
2026ECIRThe Third Search Futures Workshop at ECIR'26.Leif Azzopardi, Charles L. A. Clarke, Claudia Hauff, Yubin Kim, Zhaochun Ren, Adam Roegiest, Johanne R. Trippas, Saber Zerhoudi
2025ACLEvaluation of Attribution Bias in Generator-Aware Retrieval-Augmented Large Language Models.Amin Abolghasemi, Leif Azzopardi, Seyyed Hadi Hashemi, Maarten de Rijke, Suzan Verberne
2025CHIIRAssessing Risks in Online Information Sharing.Leif Azzopardi, Emma Nicol, Jo Briggs, Wendy Moncur, Burkhard Schafer, Callum Nash, Melissa Duheric
2025CHIIRSearch Changes Consumers' Minds: How Recognizing Gaps Drives Sustainable Choices: How Recognizing Gaps Drives Sustainable Choices.Frans van der Sluis, Leif Azzopardi
2025ECIRImproving the Reusability of Conversational Search Test Collections.Zahra Abbasiantaeb, Chuan Meng, Leif Azzopardi, Mohammad Aliannejadi
2025EMNLPPOW: Political Overton Windows of Large Language Models.Leif Azzopardi, Yashar Moshfeghi
2025SIGIRConversational Gold: Evaluating Personalized Conversational Search System Using Gold Nuggets.Zahra Abbasiantaeb, Simon Lupart, Leif Azzopardi, Jeffrey Dalton, Mohammad Aliannejadi
2025SIGIRFrom Query to Conscience: The Importance of Information Retrieval in Empowering Socially Responsible Consumerism.Frans van der Sluis, Leif Azzopardi, Florian Meier
2024CHIIRSearch under Uncertainty: Cognitive Biases and Heuristics - Tutorial on Modeling Search Interaction using Behavioral Economics.Leif Azzopardi, Jiqun Liu
2024CHIIRSeeking Socially Responsible Consumers: Exploring the Intention-Search-Behaviour Gap.Leif Azzopardi, Frans van der Sluis
2024CHIIRThe Influence of Presentation and Performance on User Satisfaction.Kanaad Pathak, Leif Azzopardi, Martin Halvey
2024CHIIRUncharted Territory: Understanding Exploratory Search Behaviours in Literature Reviews.Ayah Soufan, Ian Ruthven, Leif Azzopardi
2024ECIRMeasuring Bias in a Ranked List Using Term-Based Representations.Amin Abolghasemi, Leif Azzopardi, Arian Askari, Maarten de Rijke, Suzan Verberne
2024ECIRThe Search Futures Workshop.Leif Azzopardi, Charles L. A. Clarke, Paul B. Kantor, Bhaskar Mitra, Johanne R. Trippas, Zhaochun Ren
2024ECIRRanking Heterogeneous Search Result Pages Using the Interactive Probability Ranking Principle.Kanaad Pathak, Leif Azzopardi, Martin Halvey
2024SIGIRTREC iKAT 2023: A Test Collection for Evaluating Conversational and Interactive Knowledge Assistants.Mohammad Aliannejadi, Zahra Abbasiantaeb, Shubham Chatterjee, Jeffrey Dalton, Leif Azzopardi
2024SIGIRSearch under Uncertainty: Cognitive Biases and Heuristics: A Tutorial on Testing, Mitigating and Accounting for Cognitive Biases in Search Experiments.Jiqun Liu, Leif Azzopardi
2023CHIIRDriven to Distraction: Examining the Influence of Distractors on Search Behaviours, Performance and Experience.Leif Azzopardi, David Maxwell, Martin Halvey, Claudia Hauff
2023CIKMRetrievability Bias Estimation Using Synthetically Generated Queries.Amin Abolghasemi, Suzan Verberne, Arian Askari, Leif Azzopardi
2022CHIIRSearching the Literature: An Analysis of an Exploratory Search Task.Ayah Soufan, Ian Ruthven, Leif Azzopardi
2022ECIRImproving BERT-based Query-by-Document Retrieval with Multi-task Optimization.Amin Abolghasemi, Suzan Verberne, Leif Azzopardi
2022ECIRTowards Building Economic Models of Conversational Search.Leif Azzopardi, Mohammad Aliannejadi, Evangelos Kanoulas
2022SIGIRAre Taylor's Posts Risky? Evaluating Cumulative Revelations in Online Personal Data: A persona-based tool for evaluating awareness of online risks and harms.Leif Azzopardi, Jo Briggs, Melissa Duheric, Callum Nash, Emma Nicol, Wendy Moncur, Burkhard Schafer
2022SIGIRA Flexible Framework for Offline Effectiveness Metrics.Alistair Moffat, Joel Mackenzie, Paul Thomas, Leif Azzopardi
2021CHIIRCognitive Biases in Search: A Review and Reflection of Cognitive Biases in Information Retrieval.Leif Azzopardi
2021CHIIRUser Models, Metrics and Measures of Search: A Tutorial on the C/W/L Evaluation Framework.Leif Azzopardi, Alistair Moffat, Paul Thomas, Guido Zuccon
2021CHIIRInvestigating the Influence of Ads on User Search Performance, Behaviour, and Experience during Information Seeking.Olivia Foulds, Leif Azzopardi, Martin Halvey
2021CHIIRUntangling Cost, Effort, and Load in Information Seeking and Retrieval.Molly McGregor, Leif Azzopardi, Martin Halvey
2021CIKMAnalysing Mixed Initiatives and Search Strategies during Conversational Search.Mohammad Aliannejadi, Leif Azzopardi, Hamed Zamani, Evangelos Kanoulas, Paul Thomas, Nick Craswell
2021ECIRAWESSOME: An Unsupervised Sentiment Intensity Scoring Framework Using Neural Word Embeddings.Amal Htait, Leif Azzopardi
2021ICTIRERR is not C/W/L: Exploring the Relationship Between Expected Reciprocal Rank and Other Metrics.Leif Azzopardi, Joel Mackenzie, Alistair Moffat
2021ICTIRSentiment Intensity Prediction using Neural Word Embeddings.Amal Htait, Leif Azzopardi
2021ICTIRUntangling the Concept of Task in Information Seeking and Retrieval.Ayah Soufan, Ian Ruthven, Leif Azzopardi
2020CHIIRData-Driven Evaluation Metrics for Heterogeneous Search Engine Result Pages.Leif Azzopardi, Ryen W. White, Paul Thomas, Nick Craswell
2020CHIIRMade to Measure: A Workshop on Human-centred metrics for information seeking.George Buchanan, Dana McKay, Charles L. A. Clarke, Leif Azzopardi, Johanne R. Trippas
2020CHIIRReflecting upon Perceptual Speed Tests in Information Retrieval: Limitations, Challenges, and Recommendations.Olivia Foulds, Leif Azzopardi, Martin Halvey
2020HAIImpact of Agent Reliability and Predictability on Trust in Real Time Human-Agent Collaboration.Sylvain Daronnat, Leif Azzopardi, Martin Halvey, Mateusz Dubiel
2020ICTIRAnalyzing the Influence of Bigrams on Retrieval Bias and Effectiveness.Abdulaziz AlQatan, Leif Azzopardi, Yashar Moshfeghi
2020ICTIRInteractive Evaluation of Conversational Agents: Reflections on the Impact of Search Task Design.Mateusz Dubiel, Martin Halvey, Leif Azzopardi, Sylvain Daronnat
2020ICTIRUsing Sentiment Analysis for Pseudo-Relevance Feedback in Social Book Search.Amal Htait, Sbastien Fournier, Patrice Bellot, Leif Azzopardi, Gabriella Pasi
2020SIGIRPredicting Perceptual Speed from Search Behaviour.Olivia Foulds, Alessandro Suglia, Leif Azzopardi, Martin Halvey
2020SIGIRDataMirror: Reflecting on One's Data Self: A Tool for Social Media Users to Explore Their Digital Footprints.Amal Htait, Leif Azzopardi, Emma Nicol, Wendy Moncur
2019CHIBuilding Economic Models of Human Computer Interaction.Leif Azzopardi, Guido Zuccon
2019ECIRCLEF eHealth 2019 Evaluation Lab.Liadh Kelly, Lorraine Goeuriot, Hanna Suominen, Mariana L. Neves, Evangelos Kanoulas, Ren Spijker, Leif Azzopardi, Dan Li, Jimmy, Joo R. M. Palotti, Guido Zuccon
2019SIGIRBuilding Economic Models and Measures of Search.Leif Azzopardi, Alistair Moffat, Paul Thomas, Guido Zuccon
2019SIGIRcwl_eval: An Evaluation Tool for Information Retrieval.Leif Azzopardi, Paul Thomas, Alistair Moffat
2019SIGIRLooking for Opportunities: Challenges in Procurement Search.Stuart Mackie, David Macdonald, Leif Azzopardi, Yashar Moshfeghi
2018ECIRInformation Scent, Searching and Stopping - Modelling SERP Level Stopping Behaviour.David Maxwell, Leif Azzopardi
2018SIGIRMeasuring the Utility of Search Engine Result Pages: An Information Foraging Based Measure.Leif Azzopardi, Paul Thomas, Nick Craswell
2018SIGIRQuery Variation Performance Prediction for Systematic Reviews.Harrisen Scells, Leif Azzopardi, Guido Zuccon, Bevan Koopman
2017CHIIRBuilding Cost-Benefit Models of Information Interactions.Leif Azzopardi
2017CHIIRSecond International Workshop On the Evaluation of Collaborative Information Seeking and Retrieval (Ecol'17).Leif Azzopardi, Jeremy Pickens, Chirag Shah, Laure Soulier, Lynda Tamine
2017CIKMAn Empirical Analysis of Pruning Techniques: Performance, Retrievability and Bias.Ruey-Cheng Chen, Leif Azzopardi, Falk Scholer
2017CIKMIntegrating the Framing of Clinical Questions via PICO into the Retrieval of Medical Literature for Systematic Reviews.Harrisen Scells, Guido Zuccon, Bevan Koopman, Anthony Deacon, Leif Azzopardi, Shlomo Geva
2017CIKMAlgorithmic Bias: Do Good Systems Make Relevant Documents More Retrievable?Colin Wilkie, Leif Azzopardi
2017ECIRA Task Completion Engine to Enhance Search Session Support for Air Traffic Work Tasks.Yashar Moshfeghi, Raoul Rothfeld, Leif Azzopardi, Peter Triantafillou
2017ICTIRPersonalised Search Time Prediction using Markov Chains.Vu Tran, David Maxwell, Norbert Fuhr, Leif Azzopardi
2017ICTIRAn Initial Investigation of Query Expansion Bias.Colin Wilkie, Leif Azzopardi
2017SIGIRThe Lucene for Information Access and Retrieval Research (LIARR) Workshop at SIGIR 2017.Leif Azzopardi, Matt Crane, Hui Fang, Grant Ingersoll, Jimmy Lin, Yashar Moshfeghi, Harrisen Scells, Peilin Yang, Guido Zuccon
2017SIGIRExploring the Query Halo Effect in Site Search: Leading People to Longer Queries.Djoerd Hiemstra, Claudia Hauff, Leif Azzopardi
2017SIGIRA Study of Snippet Length and Informativeness: Behaviour, Performance and User Experience.David Maxwell, Leif Azzopardi, Yashar Moshfeghi
2017SIGIRA Test Collection for Evaluating Retrieval of Studies for Inclusion in Systematic Reviews.Harrisen Scells, Guido Zuccon, Bevan Koopman, Anthony Deacon, Leif Azzopardi, Shlomo Geva
2016CHIIRImpacts of Time Constraints and System Delays on User Experience.Anita Crescenzi, Diane Kelly, Leif Azzopardi
2016CIKMAgents, Simulated Users and Humans: An Analysis of Performance and Behaviour.David Maxwell, Leif Azzopardi
2016ECIRTwo Scrolls or One Click: A Cost Model for Browsing Search Results.Leif Azzopardi, Guido Zuccon
2016ICTIRAdvances in Formal Models of Search and Search Behaviour.Leif Azzopardi, Guido Zuccon
2016ICTIRAn Analysis of the Cost and Benefit of Search Interactions.Leif Azzopardi, Guido Zuccon
2016ICTIRA Topical Approach to Retrievability Bias Estimation.Colin Wilkie, Leif Azzopardi
2016SIGIRSimulation of Interaction: A Tutorial on Modelling and Simulating User Interaction and Search Behaviour.Leif Azzopardi
2016SIGIRSimulating Interactive Information Retrieval: SimIIR: A Framework for the Simulation of Interaction.David Maxwell, Leif Azzopardi
2016SIGIRInfoScout: An Interactive, Entity Centric, Person Search Tool.Sean McKeown, Martynas Buivys, Leif Azzopardi
2015ADCSIntegrating and Evaluating Neural Word Embeddings in Information Retrieval.Guido Zuccon, Bevan Koopman, Peter Bruza, Leif Azzopardi
2015CIKMECol 2015: First international workshop on the Evaluation on Collaborative Information Seeking and Retrieval.Leif Azzopardi, Jeremy Pickens, Tetsuya Sakai, Laure Soulier, Lynda Tamine
2015CIKMSearching and Stopping: An Analysis of Stopping Rules and Strategies.David Maxwell, Leif Azzopardi, Kalervo Jrvelin, Heikki Keskustalo
2015CIKMQuery Length, Retrievability Bias and Performance.Colin Wilkie, Leif Azzopardi
2015ECIRA Tutorial on Measuring Document Retrievability.Leif Azzopardi
2015ECIRA Game of Search.Leif Azzopardi
2015ECIRThe Impact of Query Interface Design on Stress, Workload and Performance.Ashlee Edwards, Diane Kelly, Leif Azzopardi
2015ECIRRetrievability and Retrieval Bias: A Comparison of Inequality Measures.Colin Wilkie, Leif Azzopardi
2015ICTIRTheory of Retrieval: The Retrievability of Information.Leif Azzopardi
2015ICTIRAn Analysis of Theories of Search and Search Behavior.Leif Azzopardi, Guido Zuccon
2015SIGIRBuilding and Using Models of Information Seeking, Search and Retrieval: Full Day Tutorial.Leif Azzopardi, Guido Zuccon
2015SIGIRTime Pressure and System Delays in Information Search.Anita Crescenzi, Diane Kelly, Leif Azzopardi
2015SIGIRUntangling Result List Refinement and Ranking Quality: a Framework for Evaluation and Prediction.Jiyin He, Marc Bron, Arjen P. de Vries, Leif Azzopardi, Maarten de Rijke
2015SIGIRHow many results per page?: A Study of SERP Size, Search Behavior and User Experience.Diane Kelly, Leif Azzopardi
2015SIGIRAn Initial Investigation into Fixed and Adaptive Stopping Strategies.David Maxwell, Leif Azzopardi, Kalervo Jrvelin, Heikki Keskustalo
2014CIKMA Retrievability Analysis: Exploring the Relationship Between Retrieval Bias and Retrieval Performance.Colin Wilkie, Leif Azzopardi
2014ECIRPageFetch 2: gamification the sequel.Leif Azzopardi, Martin Bevc, Andrew Gardner, David Maxwell, Abdullah Razzouk
2014ECIRPage Retrievability Calculator.Leif Azzopardi, Rosanne English, Colin Wilkie, David Maxwell
2014ECIRStudying user browsing behavior through gamified search tasks.Jiyin He, Marc Bron, Leif Azzopardi, Arjen P. de Vries
2014ECIRBest and Fairest: An Empirical Analysis of Retrieval System Bias.Colin Wilkie, Leif Azzopardi
2014ECIREfficiently Estimating Retrievability Bias.Colin Wilkie, Leif Azzopardi
2014SIGIRModelling interaction with economic models of search.Leif Azzopardi
2014SIGIRThe retrievability of documents.Leif Azzopardi
2013ADCSEconomic models of search.Leif Azzopardi
2013CIKMHigh throughput filtering using FPGA-acceleration.Wim Vanderbauwhede, Anton Frolov, Leif Azzopardi, Sai Rahul Chalamalasetti, Martin Margala
2013ECIRRe-leashed! The PuppyIR Framework for Developing Information Services for Children, Adults and Dogs.Douglas Dowie, Leif Azzopardi
2013ECIRReducing the Uncertainty in Resource Selection.Ilya Markov, Leif Azzopardi, Fabio Crestani
2013ECIRAn Initial Investigation on the Relationship between Usage and Findability.Colin Wilkie, Leif Azzopardi
2013SIGIRHow query cost affects search behavior.Leif Azzopardi, Diane Kelly, Kathy Brennan
2013SIGIR#trapped!: social media search system requirements for emergency management professionals.Stefan Raue, Leif Azzopardi, Christopher W. Johnson
2013SIGIRRelating retrievability, performance and length.Colin Wilkie, Leif Azzopardi
2012ECIREmSe: Supporting Children's Information Needs within a Hospital Environment.Leif Azzopardi, Douglas Dowie, Sergio Duarte Torres, Carsten Eickhoff, Richard Glassey, Karl Gyllstrom, Djoerd Hiemstra, Franciska de Jong, Frea Kruisinga, Kelly Ann Marshall, Sien Moens, Tamara Polajnar, Frans van der Sluis, Arjen P. de Vries
2012ECIRCrisees: Real-Time Monitoring of Social Media Streams to Support Crisis Management.David Maxwell, Stefan Raue, Leif Azzopardi, Christopher W. Johnson, Sarah Oates
2012ECIRDetection of News Feeds Items Appropriate for Children.Tamara Polajnar, Richard Glassey, Leif Azzopardi
2012ECIRTop-k Retrieval Using Facility Location Analysis.Guido Zuccon, Leif Azzopardi, Dell Zhang, Jun Wang
2012SIGIRALF: a client side logger and server for capturing user interactions in web applications.Leif Azzopardi, Myles Doolan, Richard Glassey
2012SIGIRYooSee: a video browsing application for young children.Leif Azzopardi, Douglas Dowie, Kelly Ann Marshall
2012SIGIRMaSe: create your own mash-up search interface.Leif Azzopardi, Douglas Dowie, Kelly Ann Marshall, Richard Glassey
2012SIGIRPageFetch: a retrieval game for children (and adults).Leif Azzopardi, James Purvis, Richard Glassey
2011CIKMFu-Finder: a game for studying querying behaviours.Carly O'Neil, James Purvis, Leif Azzopardi
2011ECIRBack to the Roots: Mean-Variance Analysis of Relevance Estimations.Guido Zuccon, Leif Azzopardi, Keith van Rijsbergen
2011ICTIRAn Analysis of Ranking Principles and Retrieval Strategies.Guido Zuccon, Leif Azzopardi, C. J. van Rijsbergen
2011ICTIROn the use of Complex Numbers in Quantum Models for Information Retrieval.Guido Zuccon, Benjamin Piwowarski, Leif Azzopardi
2011SIGIRThe economics in interactive information retrieval.Leif Azzopardi
2011SIGIRJuSe: a picture dictionary query system for children.Tamara Polajnar, Richard Glassey, Leif Azzopardi
2011SIGIRThe interactive PRP for diversifying document rankings.Guido Zuccon, Leif Azzopardi, C. J. van Rijsbergen
2010CIKMA comparison of user and system query performance predictions.Claudia Hauff, Diane Kelly, Leif Azzopardi
2010ECIRQuery Performance Prediction: Evaluation Contrasted with Effectiveness.Claudia Hauff, Leif Azzopardi, Djoerd Hiemstra, Franciska de Jong
2010ECIRA Case for Automatic System Evaluation.Claudia Hauff, Djoerd Hiemstra, Leif Azzopardi, Franciska de Jong
2010ECIRUsing the Quantum Probability Ranking Principle to Rank Interdependent Documents.Guido Zuccon, Leif Azzopardi
2010SIGIROn the relationship between effectiveness and accessibility.Leif Azzopardi, Richard Bache
2010SIGIRImproving sentence retrieval with an importance prior.Leif Azzopardi, Ronald T. Fernndez, David E. Losada
2010SIGIRSearch system requirements of patent analysts.Leif Azzopardi, Wim Vanderbauwhede, Hideo Joho
2010SIGIRFinding and filtering information for children.Desmond Elliott, Richard Glassey, Tamara Polajnar, Leif Azzopardi
2010SIGIRQuery quality: user ratings and system predictions.Claudia Hauff, Franciska de Jong, Diane Kelly, Leif Azzopardi
2010SIGIREstimating interference in the QPRP for subtopic retrieval.Guido Zuccon, Leif Azzopardi, Claudia Hauff, Keith van Rijsbergen
2010SIGIRHas portfolio theory got any principles?Guido Zuccon, Leif Azzopardi, Keith van Rijsbergen
2009CIKMUsage based effectiveness measures: monitoring application performance in information retrieval.Leif Azzopardi
2009CIKMRelying on topic subsets for system ranking estimation.Claudia Hauff, Djoerd Hiemstra, Franciska de Jong, Leif Azzopardi
2009ECIRThe Combination and Evaluation of Query Performance Prediction Methods.Claudia Hauff, Leif Azzopardi, Djoerd Hiemstra
2009FPLFPGA-accelerated Information Retrieval: High-efficiency document filtering.Wim Vanderbauwhede, Leif Azzopardi, Mahmoud Moadeli
2009ICTIRThe Quantum Probability Ranking Principle for Information Retrieval.Guido Zuccon, Leif Azzopardi, Keith van Rijsbergen
2009SIGIRQuery side evaluation: an empirical analysis of effectiveness and effort.Leif Azzopardi
2009SIGIRSearch engine predilection towards news media providers.Leif Azzopardi, Ciaran Owens
2009SIGIRDeveloping energy efficient filtering systems.Leif Azzopardi, Wim Vanderbauwhede, Mahmoud Moadeli
2009SIGIRWhen is query performance prediction effective?Claudia Hauff, Leif Azzopardi
2009SIGIREffective query expansion for federated search.Milad Shokouhi, Leif Azzopardi, Paul Thomas
2009SIGIRRevisiting logical imaging for information retrieval.Guido Zuccon, Leif Azzopardi, C. J. van Rijsbergen
2008CIKMRetrievability: an evaluation measure for higher order information access tasks.Leif Azzopardi, Vishwa Vinay
2008CIKMRevisiting the relationship between document length and relevance.David E. Losada, Leif Azzopardi, Mark Baillie
2008ECIRAccessibility in Information Retrieval.Leif Azzopardi, Vishwa Vinay
2008WWWResolving Person Names in Web People Search.Krisztian Balog, Leif Azzopardi, Maarten de Rijke
2007ECIRA Retrieval Evaluation Methodology for Incomplete Relevance Assessments.Mark Baillie, Leif Azzopardi, Ian Ruthven
2007SIGIRBuilding simulated queries for known-item topics: an analysis using six european languages.Leif Azzopardi, Maarten de Rijke, Krisztian Balog
2007SIGIRBroad expertise retrieval in sparse data environments.Krisztian Balog, Toine Bogers, Leif Azzopardi, Maarten de Rijke, Antal van den Bosch
2007SIGIRIntra-assessor consistency in question answering.Ian Ruthven, Leif Azzopardi, Mark Baillie, Ralf Bierig, Emma Nicol, Simon O. Sweeney, Murat Yakici
2007SIGIRUpdating collection representations for federated search.Milad Shokouhi, Mark Baillie, Leif Azzopardi
2006ECIRAn Efficient Computation of the Multiple-Bernoulli Language Model.Leif Azzopardi, David E. Losada
2006SACAn evaluation of resource description quality measures.Mark Baillie, Leif Azzopardi, Fabio Crestani
2006SIGIRAdaptive query-based sampling for distributed IR.Leif Azzopardi, Mark Baillie, Fabio Crestani
2006SIGIRAutomatic construction of known-item finding test beds.Leif Azzopardi, Maarten de Rijke
2006SIGIRFormal models for expert finding in enterprise corpora.Krisztian Balog, Leif Azzopardi, Maarten de Rijke
2006SPIREAdaptive Query-Based Sampling of Distributed Collections.Mark Baillie, Leif Azzopardi, Fabio Crestani
2005ECIRAge Dependent Document Priors in Link Structure Analysis.Claudia Hauff, Leif Azzopardi
2005SIGIRProbabilistic hyperspace analogue to language.Leif Azzopardi, Mark A. Girolami, Malcolm K. Crowe
2004IJCNNTopic based language models for ad hoc information retrieval.Leif Azzopardi, Mark Girolami, C. J. van Rijsbergen
2004SIGIRUser biased document language modelling.Leif Azzopardi, Mark A. Girolami, Cornelis Joost van Rijsbergen
2003SIGIRInvestigating the relationship between language model perplexity and IR precision-recall measures.Leif Azzopardi, Mark A. Girolami, Keith van Rijsbergen