This program calculates ^{3}*J*_{HH} values according to
the Karplus equation

* J = A cos^{2}(d) - B cos(d) + C*,

^{*}
the coefficients are taken from Haasnoot et al. 1980 Tetrahedron paper.
If more precision is needed, the paper offers
a variation of the Karplus equation, which
takes into account electronegativities:

"The relationship between proton-proton nmr coupling constants
and substituent electronegativities-I"

C.A.G. Haasnoot, F.A.A.M. DeLeeuw and C. Altona

*Tetrahedron* **1980**, *36*, 2783-2792