P. H\aandlykken, und K. Nygaard. Software Engineering Environments Proceedings of the
Symposium held in Lahnstein, Germany, June 16-20, 1980, Amsterdam, North-Holland, (1981)
K. Nygaard. Information Processing 86, Seite 189--198. North-Holland, IFIP, Elsevier Science Publishers B.V., (September 1986)http://www.ifi.uio.no/~kristen/PDF_MAPPE/F_PDF_MAPPE/F_IFIP_86.pdf
-- last visited $17^th$ November~2007.
K. Nygaard. Information Processing, Proceedings from the IFIP 10th World Computer Congress, Dublin, Irland, September 1-5, 1986, Elsevier Science Publishers B.V., North Holland, (1986)