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2. Flow diagrams, turing machines and languages with only two formation rules
3. {IBM74} IBM System/360 and System/370 FORTRAN IV Language (GC28--6515--0); May 1974; page 42. {IBM74} IBM System/360 and System/370 FORTRAN IV Language (GC28--6515--0); May 1974; page 42.
4. {Your75} Yourdon Edward; Techniques of Program Structure and Design; Prentice-Hall; Englewood Cliffs NJ; 1975. {Your75} Yourdon Edward; Techniques of Program Structure and Design; Prentice-Hall; Englewood Cliffs NJ; 1975.