  This paper deals with the spectral problem of the Manakov Santini system. The
point Lie symmetries of the Lax pair have been identified. Several similarity
reductions arise from these symmetries. An important benefit of our procedure
is that the study of the Lax pair instead of the partial differential equations
yields the reductions of the eigenfunctions and also the spectral parameter.
Therefore, we have obtained five interesting spectral problems in 1+1
dimensions.
