### multivariable taylor series

I know how to generate a multivairiable Taylor series and extract its coefficients. What I want to do is to extract all the terms where the exponents of the individual variables satisfy certain requirements.

So for instance, my function is
f(x,y)=(1/(1-x*y))*(1/(1-x*y^2))*(1/(1-x*y^3))*(1-x*y^4))

What I want is all terms in the Taylor series such that the exponent on x is at most 10 and the exponent on y is at most 20. Ideas?