TOMS419 is a FORTRAN77 library which implements ACM TOMS algorithm 419, which seeks the roots of a polynomial with complex coefficients.
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. in.
TOMS419 is available in a FORTRAN77 version.
BRENT, a FORTRAN77 library which contains Richard Brent's routines for finding the zero, local minimizer, or global minimizer of a scalar function of a scalar argument, without the use of derivative information.
TEST_ZERO, a FORTRAN90 library which defines some test functions for which zeroes can be sought.
TOMS365,
a FORTRAN77 library which
finds a root of an analytic complex function
by the downhill method;
this is a FORTRAN77 version of ACM TOMS algorithm 365.
TOMS429,
a FORTRAN77 library which
reports information about the estimated location
of roots of a polynomial;
this is ACM TOMS algorithm 429.
TOMS493,
a FORTRAN77 library which
seeks the roots of a real polynomial;
this library is commonly called RPOLY;
this is ACM TOMS algorithm 493.
ZOOMIN, a FORTRAN90 library which includes various zero finder routines.
Michael Jenkins, Joseph Traub
You can go up one level to the FORTRAN77 source codes.