Sorting routines in Fortran 77 by G. T. Houlsby and S. W. Sloan
A full description is published in
Houlsby, G. T., & Sloan, S. W. (1984). Efficient sorting routines in FORTRAN 77. Advances in Engineering Software (1978), 6(4), 198-203. https://doi.org/10.1016/0141-1195(84)90004-4