What is the fine-grained topic of the following text: Serena Cicalò would like to thank the Centro de Álgebra da Universidade de Lisboa for their kind hospitality during July - December 2009 and May - September 2010, when the classification of the 6-dimensional nilpotent Lie algebras over fields of characteristic 2 was made and added to the package. Only return the topic.
Classification of 6-dimensional nilpotent Lie algebras over fields of characteristic 2