@inproceedings{DBLP:conf/caap/Ehrig81,
  author    = {Hartmut Ehrig},
  title     = {Algebraic Theory of Parameterized Specifications with Requirements},
  booktitle = {CAAP},
  year      = {1981},
  pages     = {1-24},
  ee        = {http://dx.doi.org/10.1007/3-540-10828-9_51},
  crossref  = {DBLP:conf/caap/1981},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

@proceedings{DBLP:conf/caap/1981,
  editor    = {Egidio Astesiano and
               Corrado B{\"o}hm},
  title     = {CAAP '81, Trees in Algebra and Programming, 6th Colloquium,
               Genoa, Italy, March 5-7, 1981, Proceedings},
  booktitle = {CAAP},
  publisher = {Springer},
  series    = {Lecture Notes in Computer Science},
  volume    = {112},
  year      = {1981},
  isbn      = {3-540-10828-9},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}