  For the algebra L= K <x, d/dx, \int> of polynomial integro-differential
operators over a field K of characteristic zero, a classification of
indecomposable, generalized weight L-modules of finite length is given. Each
such module is an infinite dimensional uniserial module. Ext-groups are found
between indecomposable generalized weight modules, it is proven that they are
finite dimensional vector spaces.
