@article {baerland2019multigrid,
	title = {Multigrid Methods for Discrete Fractional Sobolev Spaces},
	journal = {SIAM Journal on Scientific Computing},
	volume = {41},
	number = {2},
	year = {2019},
	pages = {A948{\textendash}A972},
	publisher = {{SIAM},
	author = {B{\ae}rland, Trygve and Kuchta, Miroslav and Mardal, Kent-Andre}
}
