  We comment on a recent paper by Chen, Liu, and Ge (J. Phys. A: Math. Gen. 31
(1998) 6473), wherein a nonlinear deformation of su(1,1) involving two
deforming functions is realized in the exactly solvable quantum-mechanical
problem with P\" oschl-Teller potential, and is used to derive the well-known
su(1,1) spectrum-generating algebra of this problem. We show that one of the
defining relations of the nonlinear algebra, presented by the authors, is only
valid in the limiting case of an infinite square well, and we determine the
correct relation in the general case. We also use it to establish the correct
link with su(1,1), as well as to provide an algebraic derivation of the
eigenfunction normalization constant.
