  The function $$W(aq,b)=\int\int_0^{2\pi}\ln[1-a\cos x-b\cos
y-(1-a-b)\cos(x+y)]dxdy$$ which expresses the spanning-tree entropy for various
two dimensional lattices, for example, is evaluated directly in terms of
standard functions. It is applied to derive several limiting values of the
triangular lattice Green function.
