Leif Azzopardi, Benno Stein, Norbert Fuhr, Philipp Mayr, Claudia Hauff, Djoerd Hiemstra: Advances in Information Retrieval - 41st European Conference on IR Research, ECIR 2019, Cologne, Germany, April 14-18, 2019, Proceedings, Part II. Lecture Notes in Computer Science 11438, Springer 2019, ISBN 978-3-030-15718-0