An algebra of boundary value problems for a class of pseudodifferential operators of variable order

An algebra is constructed containing the operators of boundary value problems for pseudodifferential operators which are formally hypoelliptic in the sense of Hörmander and elliptic at points of the boundary; parametrices for these boundary value problems are also constructed. The Fredholm property is demonstrated in a scale of weighted spaces, based on $L_p$, $1<p<\infty$, and the index is computed.