LAPACK is an excellent set of linear algebra routines in Fortran: eigenvalues and vectors, various matrix operations, etc. Some people in the know say it's better than LINPACK and EISPACK. You can get source and manpages at ftp://netlib.att.com/netlib/lapack There is also a helpful manual available from SIAM. The lapack.c file utilizes LAPACK to do things like matrix inversion. Of course, you do not have to know LAPACK in order to understand functions like MatrixInvert, which can be treated as black boxes (it inverts matrices, really!).