My guess is that "sortqx" was a library routine and not a statement. It is not standard Fortran. I can find a reference to a routine by that name in the old Compaq Extended Math Library, but that is not available to you. Intel MKL does not appear to have such a routine.
Intel Visual Fortran provides QSORT and SORTQQ library routines which does ordinary sorting, but not an index sort. IMSL also has a collection of sorting routines, but none of them appear to be index sorts (also known as "tag sort".)
Unless you can find a compatible routine source somewhere, you will probably have to rewrite that part of the code to use a normal sort.
