Chinese Quadruple Radicals
By Jennifer Ball and Maggie Li (李琪)
Quadruple radicals are not common, but they do give a sense of what one character means four times. If X = n, then 4X = 4n: we have a better sense about what a character means when its effect is replicated four times.
http://wenwen.soso.com/z/q72827090.htm (translated via Google webpage translation)
McNaughton, William and Li Ying. Reading and writing Chinese: a guide to the Chinese writing system, the student’s 1,020 list, the official 2,000 list. Ruttland, VT: Charles E. Tuttle, 1999.