Don't have the original paper ... but once you have the decomposition into shears I don't really see why you need more information.
First shear : x' = x - tan (theta/2) * y
Second shear : y' = y + sin(theta) * x
Third shear : x' = x - tan (theta/2) * y
Everything else follows from that.
Netpbm and Freeimage implement the algorithm too BTW.
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