Na podstawie prac:<br />
Z. Ciesielski, <i>Orthogonal projections onto spline spaces with arbitrary
knots</i>. Function spaces (Poznań, 1998), 133-140, Lecture Notes in Pure
and Appl. Math., 213,<br />
M.Passenbrunner, A.Shadrin, <i>On almost everywhere convergence of
orthogonal spline projections with arbitrary knots</i>, preprint 2013,
arXiv:1308.4824.