Celt references *Crane, H. Richard, "How Things Work: The Rattleback Revisited" TPT 29(5), 278-279, (May 1991). *Edge, Ronald D. and Richard Childers, "String and Sticky Tape: Curious Celts and Riotous Rattlebacks" TPT 37(2), 80, (Feb 1999) *Walker, Jearl , "Rattlebacks and Tippe Tops" in "Roundabout: The Physics Of Rotation in the Everyday World", 33-38 (from the Amateur Scientist, Scientific American Oct 1979, 172) *Pippard, AB, "How to make a celt or rattleback", Eur J Phys 11, 63-4, (1990) *Bondi, Sir Hermann, "The rigid body dynamics of unidirectional spin", Proc R Soc Lond A 405, 265-74, (1986) Walgate, Robert, Tops That Like to Spin One Way, Nature Vol 323, 204, (18 Sept. 1986) - a notice of Bondi's article Not seen: H. Crabtree, An Elementary Treatment of the Spinning Tops and Gyroscopic Motion, Chelsea, NY., (1967) -Walker refers tothis but it isn't at SFU Allan J. Boardman, The Mysterious Celt; Fine Woodworking No. 53, 68-69, (July/Aug 1985).