References

The original implementation is documented fairly thoroughly in Georg Schreckenbach's Ph.D. thesis (University of Calgary, 1996), which is available at http://www.scm.com/Doc/publist.html, as well as in the following papers:

G. Schreckenbach and Tom Ziegler,
[5] J Phys Chem 1995, 99, 606. (NMR all-electron formulation)
[6] Int J Quantum Chem 1996, 60, 753. (frozen core approximation)
[7] Int J Quantum Chem 1997, 61, 899. (scalar relativistic method
[8] J Phys Chem A 1997, 101, 3388. (ESR g-tensor)

[9] Patchkovskii, S.; Ziegler, T. J Phys Chem 2001, A105, 5490. (High-spin EPR g-tensor)

There are also various application papers published. These papers illustrate some of the concepts and functionality that is described here.