Wolfgang Henhapl Cliff B. Jones A Formal Definition of Algol 60 as Described in the 1975 Modified Report. 305-336 1978 conf/fm/1978 The Vienna Development Method: The Meta-Language db/conf/fm/vdm1978.html#HenhaplJ78 http://dx.doi.org/10.1007/3-540-08766-4_12