12H-dibenzo[d,g][1,3,2]dioxaphosphocins: Synthesis, structures and “through-space” spin-spin coupling in their NMR spectra. John D. Goddard1, Alan W. Payne1, Nick Cook, Henry R. Luss. Journal of Heterocyclic Chemistry. Volume 25, Issue 2, pages 575–588, March/April 1988