van den Brand, M. G. J., N. W. P. van Diepen, E. A. Boiten, C. H. A. Koster, H. A. Partsch, and N. Völker. 1991. “USTOPIA REQUIREMENTS THOUGHTS ON A USER-FRIENDLY SYSTEM FOR TRANSFORMATION OF PROGRAMS IN ABSTRACTO”. Periodica Polytechnica Electrical Engineering 35 (2):101-23.