@article {GronlundWSR90,
	title = {Constrained spin model of phason dynamics in quasi-crystals},
	journal = {Physical Review B},
	volume = {42},
	year = {1990},
	pages = {8517-8536},
	author = {Gronlund, L. D. and Wright, D. C. and Sethna, J. P. and Rokhsar, D. S.}
}
