@article {aja2008matrix,
	title = {Matrix modeling of hierarchical fuzzy systems},
	journal = {Fuzzy Systems, IEEE Transactions on},
	volume = {16},
	number = {3},
	year = {2008},
	pages = {585{\textendash}599},
	publisher = {IEEE},
	author = {Santiago Aja-Fern{\'a}ndez and Carlos Alberola-Lopez}
}
