@article {D:nhpc1,
	title = {Natural Heuristics for Proof Construction. {P}art {I}: Classical Propositional Logic},
	journal = {Logique et Analyse},
	volume = {32},
	number = {127-128},
	year = {1989},
	note = {Appeared 1992},
	pages = {337{\textendash}363},
	author = {Batens, Diderik}
}
