1. USA Standard FORTRAN, USASX3.9-1966, Section 7.2.3.8., USA Standards Institute, New York.
2. USA Standard FORTRAN, Appendix B, Section 1.1
3. USA Standard FORTRAN, Section 4.
4. USA Standard FORTRAN, Section 5.3.
5. USA Standard FORTRAN, Section 5.1.3.3.