@article{1997-Proper-Versions,
  author		= "{Proper}, H.A. (Erik)",
  title			= "{Data Schema Design as a Schema Evolution Process}",
  journal		= "Data {\&} Knowledge Engineering",
  number		= "2",
  volume		= "22",
  year			= "1997",
  research_group	= "iris",
  pages			= "159--189",
  class			= "Journal"
}