@techreport{HH:sizes,
  author      = {J. Hage and T. Harju},
  title       = {The size of 2-classes in group labeled 2-structures},
  url         = {http://www.wi.leidenuniv.nl/TechRep/tr96-17.html},
  institution = {Leiden University, Department of Computer Science},
  year        = {1996},
  number      = {17},
  pubcat      = {techreport},
  note        = {Generalized in \cite{HH:sizesrev}},
}