Context: Works published since 1857 have received alternative catalogue designations instead of opus numbers. The present standard musicological reference for Chopin's works is the Kobylańska Catalogue (usually represented by the initials 'KK'), named for its compiler, the Polish musicologist Krystyna Kobylańska.

Question: The Kobylańska Catalogue was named for who?
Answer: Krystyna Kobylańska

Question: Pieces published after what year stopped receiving opus numbers?
Answer: 1857

Question: What have pieces published after 1857 been given rather than opus numbers?
Answer: alternative catalogue designations

Question: What is the current musicologist reference for Chopin's pieces?
Answer: the Kobylańska Catalogue

Question: What is the shortened reference for the Kobylańska Catalogue?
Answer: KK

Question: Who compiled the Kobylańska Catalogue?
Answer: Krystyna Kobylańska.