R. D. Grigorieff, Ian H. Sloan. Discrete orthogonal projections on multiple knot periodic splines. Journal of Approximation Theory, 137(2):201-225, 2005. [doi]
@article{GrigorieffS05,
title = {Discrete orthogonal projections on multiple knot periodic splines},
author = {R. D. Grigorieff and Ian H. Sloan},
year = {2005},
doi = {10.1016/j.jat.2005.09.003},
url = {http://dx.doi.org/10.1016/j.jat.2005.09.003},
researchr = {https://researchr.org/publication/GrigorieffS05},
cites = {0},
citedby = {0},
journal = {Journal of Approximation Theory},
volume = {137},
number = {2},
pages = {201-225},
}