The library fflas-ffpack is a library for dense and sparse linear algebra over a finite field or the ring of integers, available from https://github.com/linbox-team/fflas-ffpack.
The source of this document is in /build/reproducible-path/macaulay2-1.25.05+ds/M2/Macaulay2/packages/Macaulay2Doc/ov_preface.m2:122:0.