  We define an embedding of the space of complex momenta and masses in
perturbation theory into a universal projective space. This embedding is
natural in the sense of properties of the vector bundle defined by Feynman
integrals on the complement to Landau varieties. We point out that there is a
holonomic D-module associated with individual Feynman integrals. We quote
explicit generators for this D-module on the fully deformed space of particle
momenta. This basis is quadratic in the derivatives. We conclude that there is
holonomic D-module on the physical space of momenta.
