A Search Tool for Corpora with Positional Tagsets and Ambiguities. - Adam Przepiórkowski; Zygmunt Krynicki; Lukasz Debowski; Marcin Wolinski; Daniel Janus; Piotr Banski (LREC, 2004)

Poliqarp: An open source corpus indexer and search engine with syntactic extensions. - Daniel Janus; Adam Przepiórkowski (ACL, 2007)