Feliks Kluzniak Miroslawa Milkowska Readable, Runnable Requirements Specifications in SPILL-2. 449-450 1994 conf/plilp/1994 PLILP db/conf/plilp/plilp94.html#KluzniakM94 http://dx.doi.org/10.1007/3-540-58402-1_32