@techreport{Smolka89,
  author	= {Smolka, Gert},
  year		= {1989},
  title		= {A feature logic with subsorts},
  number	= {LILOG Report, 33},
  note		= {(To appear in the Proceedings of the Workshop on Unification Formalisms -- Syntax, Semantics, and Implementation, Titisee, The MIT Press, 1990.)},
  institution	= {IWBS, IBM Deutschland, Postfach 80 08 80, Stuttgart}
}