I stopped at page 1-21:
‘From the complete energy matrix it can be derived that under the so-called weak-field limit
(Zeeman interaction << zero-field interaction) the three elements of the real g tensor…can be fixed at 2.00 and that the shape of the EPR spectra, the effective g values, is a function of the
rhombicity E/D.’
I don’t see why this is the case