  The general approach for describing systems with Bose-Einstein condensate,
where atoms interact through nonlocal pair potentials, is presented. A special
attention is paid to nonintegrable potentials, such as the dipolar interaction
potential. The potentials that are not absolutely integrable can have not well
defined Fourier transforms. Using formally such not defined Fourier transforms
leads to unphysical conclusions. For making the Fourier transform well defined,
the interaction potential has to be regularized. This is illustrated by the
example of dipolar interactions.
