  The kinematical constraints of pair operators in nuclear collective motion,
pointed out by Yamamura and identified by Nishiyama as relations between so(2n)
generators, are recognized as equations satisfied by second-degree annihilators
(deduced in previous work) of irreducible so(2n)-modules. The recursion
relations for Nishiyama's tensors and their dependence on the parity of the
tensor degree are explained. An explanation is also given for the recursion
relation for the sp(2n) tensors pointed out by Hwa and Nuyts. The statements
for the algebras so(2n) and sp(2n) are proved simultaneously.
