@article{foster:011803,
	Author = {David H. Foster and Andrew K. Cook and Jens U. N{\"o}ckel},
	Journal = {Physical Review A (Atomic, Molecular, and Optical Physics)},
	Number = {1},
	Pages = {011803},
	Title = {Degenerate perturbation theory describing the mixing of orbital angular momentum modes in Fabry-Perot cavity resonators},
	Volume = {79},
	Year = {2009}}