Advances in Information Retrieval 41st European Conference on IR Research, ECIR 2019, Cologne, Germany, April 14-18, 2019, Proceedings, Part I - Azzopardi, Leif; Azzopardi, Leif; Stein, Benno; Stein, Benno; Fuhr, Norbert; Fuhr, Norbert; Mayr, Philipp; Mayr, Philipp; Hauff, Claudia; Hauff, Claudia; Hiemstra, Djoerd; Hiemstra, Djoerd (Springer International Publishing : Imprint: Springer, 2019)