Reduced Vectorial Ribaucour Transformation for the Darboux-Egoroff   Equations
  The vectorial fundamental transformation for the Darboux equations is reduced to the symmetric case. This is combined with the orthogonal reduction of Lame type to obtain those vectorial Ribaucour transformations which preserve the Egoroff reduction. We also show that a permutability property holds for all these transformations. Finally, as an example, we apply these transformations to the Cartesian background. 
Q. P. Liu and M. Manas