Abstract : Institutional repositories have spread in universities where they provide services for recording, distributing, and preserving the institution's intellectual output. When the Lausanne "academic server", named SERVAL, was launched at the end of 2008, the Faculty of Biology and Medicine addressed from the outset the issue of quality of metadata. Accuracy is fundamental since research funds are allocated on the basis of the statistics and indicators provided by the repository. The Head of faculty also charged the medical library to explore different ways to measure and assess the research output. The first step for the Lausanne university medical library was to implement the PubMed and the Web of Science web services to easily extract clean bibliographic information from the databases directly into the repository. Now the medical library is testing other web services (from CrossRef, Web of Science, etc.) to generate quantitative data on research impact mainly. The approach is essentially based on citation linking. Although the utility of citation and bibliometric evaluation is still debated, the most prevalent output measures used for research evaluation are still those based on citation analysis. Even when a new scientific evaluation indicator is proposed, such as h-index, we can always see its link with citation. Additionally, the results of a new indicator are often compared with citation analysis. The presentation will review the web services which might be used in institutional repositories to collect and aggregate citation information for the researchers' publications.