@article {Ferrari:November 2001:0195-6698:1059,
	author = "Ferrari L.",
	title = "Polynomial Rings in Which Delta Operators are Derivations",
	journal = "European Journal of Combinatorics",
	volume = "22",
	year = "November 2001",
	abstract = "<P>For each delta operator <B>Q</B>, we define a multiplication of polynomials of <B>K</B> [ <B>x</B>] that makes <B>Q</B> a derivation in a suitable polynomial ring. We see that such derivation ring is isomorphic to <B>K</B> [<B>x</B> ] with the usual derivative operator <B>D</B>. We supply a complete classification of the isomorphisms between these two structures, ending with a slight generalization. <B>Copyright 2001 Academic Press</B></P>",
	pages = "1059-1064(6)",
	url = "http://www.ingentaconnect.com/content/ap/ej/2001/00000022/00000008/art00534"
}