@article {WheelerTiefelsdorf2005JGS,
	title = {{Multicollinearity and correlation among local regression coefficients in geographically weighted regression}},
	journal = {Journal of Geographical Systems},
	volume = {7},
	year = {2005},
	pages = {161-187},
	author = {Wheeler, D. and Tiefelsdorf, M.}
}