good material for understanding graph reduction?

[Ahn Ki-yung]

There are lot of materaials - from class tutorial to papers -
about classical environment based sematics or implementation.
Related to lazy languages I found these two articles very much
helpful to understand the semantics and implementation via
evironment-based evauation model.

* Deriving a Lazy Abstract Machine - Sestoft (1997)
* A Natural Semantics for Lazy Evaluation - Launchbury (1993)

There are many materials about G-machine based implementations
and supercombinator graph reuduction but not about graph
reduction itself. Reading the Wadsworth's original paper
might be good for the purpose, but unfortunately I am not
very freely accessible to good libraries now. (The paper
is quote dated, not avialable online.) So if there is
a formal/concise/illustrative/or whatsoever good meterails
about graph reduction recommend me one please.

Thanks.

p.s. My question is whetere supercombinators are
neccecery condition for graph reduction or not.