TOMS423 is a FORTRAN77 library which implements ACM TOMS algorithm 423, for Gaussian elimination to factor a matrix and solve a related linear system.
While the text of many ACM TOMS algorithms is available online through ACM: http://www.acm.org/pubs/calgo or NETLIB: http://www.netlib.org/toms/index.html, most of the early algorithms are not available. This is one of them. I typed it in.
TOMS423 is available in a FORTRAN77 version.
LAPACK_EXAMPLES, a FORTRAN77 program which demonstrates the use of the LAPACK linear algebra library.
LINPACK, a FORTRAN77 library which solves linear systems for a variety of matrix storage schemes, real or complex arithmetic, and single or double precision.
You can go up one level to the FORTRAN77 source codes.