Efficient Implementation of a Variable Projection
Algorithm for Nonlinear Least Squares Problems
Nonlinear least squares frequently arise for which
the variables to be solved for can be separated 
into a linear and a nonlinear part.  A variable projection
algorithm has been developed recently which 
is designed to take advantage of the structure of a problem
whose variables separate in this way.  This 
paper gives a slightly more efficient and slightly more
general version of this algorithm than has appeared 
earlier.
CACM March, 1974
Krogh, F. T.
