See: Forest Ray Moulton, An Introduction to Celestial Mechanics, 2nd ed. (first published by the Macmillan Company in 1914; reprinted in 1970 by Dover Publications, Inc., Mineola, New York), page 431.
Viz Forest Ray Moulton, An Introduction to Celestial Mechanics, 2nd ed. (poprvé publikováno vydavatelstvím Macmillan Company v roce 1914; reprint v roce 1970 vydalo nakladatelství Dover Publications, Inc., Mineola, New York), stránka 431.