Verse 20 contains the refrain that comes again at verse 31, and which is inserted at verse 5b in Revised Standard Version. Translators should refer to the comments regarding this refrain in Gen 10.5.
Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .