  The research monograph gives the first systematic exposition of the elliptic
(scalar and matrix) operators theory and elliptic boundary-value problems in
the scales of Hilbert spaces of H\"ormander of the functions/distributions of
arbitrary positive or negative smoothness. The book is based on the method of
interpolation with a functional parameter for the abstract and Sobolev unitary
spaces. Some results are also new for the Sobolev scales. The monograph is
intended for the researches, professors and PhD students.
