from "ELDOR Spectroscopy" by James Hyde

"There is a parallel between this article and ... saturation recovery .... Both techniques are sensitive not only to relaxation between states of an observed transition, but also to all 'other' relaxation pathways. Both have primarily been used in the past for relaxometry. Saturation recovery is sensitive to the disappearance of magnetization because of saturation transfer, and ELDOR is sensitive to consequent appearance of magnetisation elsewhere in the spin system. They are closely related, but because they have differing sensitivities to the transverse relaxation mechanisms, use of them together in a dual manner is appropriate. The author is convinced that molecular biology, ELDOR, and saturation recovery in concert provide the basis for a true spectroscopy for the study of complex biological systems based on nitroxide radical spin labels"

Saturation recovery is also reviewed by James Hyde in Chapter I.1, p607

Foundations of Modern EPR, G.R. Eaton, S.S. Eaton and K.M.Sakilhov World Scientific, 1997, Chapter H10, p178.