  We proved direct and inverse theorems on B-spline quasi-interpolation
sampling representation with a Littlewood-Paley-type norm equivalence in
Sobolev spaces $W^r_p$ of mixed smoothness $r$, established estimates of the
approximation error of recovery in $L_q$-norm of functions from the unit ball
$U^r_p$ in the spaces $W^r_p$ by linear sampling algorithms based on this
representation, the asymptotic optimality of these sampling algorithms in terms
of Smolyak sampling width $r^s_n(U^r_p, L_q)$ and sampling width $r_n(U^r_p,
L_q)$.
