Flemming M. Damm Bo Stig Hansen Hans Bruun On Type Checking in VDM and Related Consistency Issues. 45-62 1991 conf/fm/1991-1 VDM Europe (1) db/conf/fm/vdme1991-1.html#DammHB91 http://dx.doi.org/10.1007/3-540-54834-3_6