We provide you with a training corpus that comprises a set of author verification problems in several languages/genres. Each problem consists of some (up to five) known documents by a single person and exactly one questioned document. All documents within a single problem instance will be in the same language. However, their genre and/or topic may differ significantly. The document lengths vary from a few hundred to a few thousand words. The documents of each problem are located in a separate folder, the name of which (problem ID) encodes the language of the documents. The following list shows the available sub-corpora, including their language, type (cross-genre or cross-topic), code, and examples of problem IDs: Language; Type; Code; Problem IDs Dutch; Cross-genre; DU; DU001, DU002, DU003, etc. English; Cross-topic; EN; EN001, EN002, EN003, etc. Greek; Cross-topic; GR; GR001, GR002, GR003, etc. Spanish; Cross-genre; SP; SP001, SP002, SP003, etc. The ground truth data of the training corpus found in the file truth.txt include one line per problem with problem ID and the correct binary answer (Y means the known and the questioned documents are by the same author and N means the opposite). For example: EN001 N EN002 Y EN003 N ...