src/bvls.f
  From the source code accompanying the article 

  Stark PB, Parker RL (1995). Bounded-variable least-squares:
  an algorithm and applications, Computational Statistics, 10, 129-141,

  and downloaded from http://lib.stat.cmu.edu/general/bvls The code
  was modified slightly to allow compatibility with gfortran.  The
  authors have agreed to allow distribution under GPL version 2 or
  newer.