1. Block structure (Extended Abstract)
2. Henhapl W. and Jones G. The block concept and some possible implementations with proofs of equivalence IBM Laboratory Vienna TR 25. 104 1970. Henhapl W. and Jones G. The block concept and some possible implementations with proofs of equivalence IBM Laboratory Vienna TR 25. 104 1970.
3. IBM System/360 Operating System PL/I(F) Language Reference Manual 1969. IBM System/360 Operating System PL/I(F) Language Reference Manual 1969.