Representative organopolyphosphites contain two or more tertiary (trivalent) phosphorus atoms and may include those having the formula: wherein XI represents a substituted or unsubstituted n-valent hydrocarbon bridging radical containing from 2 to 40 carbon atoms, each R9 is the same or different and is a divalent hydrocarbon radical containing from 4 to 40 carbon atoms, each R10 is the same or di