Wiepking, C. A.; Doyle, D. V. (November 1955). Strength and related properties of Balsa and Quipo woods. UISDA Forest Service, Forest Products Laboratory, σελ. 27–28. Report No. 1511. http://ir.library.oregonstate.edu/xmlui/handle/1957/1239. The record softness of 22 lbf is often falsely ascribed to quipo, but all such reports appear to be a misreading of figures 15 and 16 from this primary source, which makes clear that measurement is of balsa, and the softest quipo measured was 46 lbf tangential, 38 lbf radial.
