Title: Coloring mixed hypergraphs
Description: http://books.google.com/books?id=RYM_Qi5HR68C&pg=PA26&dq=hypertree+hypergraph&ei=TX7vSJiuOZHEMaT4pA4&sig=ACfU3U12X-utDYS4BRfgYOOvlCAUCFV-gQ#PPP1,M1
Subjects: Hypergraphs, Map-coloring problem