"haveraged.m" is a package of the computer algebra system, Mathematica for performing necessary computations of higher-order averaging in periodically forced, weakly nonlinear systems. See the following references for the basic idea about this package and its usage: K. Yagasaki and T. Ichikawa, Higher-order averaging for periodically forced, weakly nonlinear systems, International Journal of Bifurcation and Chaos, 9 (1999), 519--531; K. Yagasaki, Detection of bifurcation structures by higher-order averaging in Duffing's equation, to appear in Nonlinear Dynamics. The preprints of these papers are available from "http://mech.gifu-u.ac.jp/~yagasaki/public_e.html". See also sample.txt for the usage. The following references include the related matters: K. Yagasaki, Higher-order averaging and ultra-subharmonics in forced oscillators, Journal of Sound and Vibration, 210 (1998), 529-553. K. Yagasaki, Higher-order averaging of strongly nonlinear oscillators using trigonometric approximations, in preparation. This package is licenced free of charge and there is absolutely no warranty. Kazuyuki Yagasaki Department of Mechanical and Systems Engineering Gifu University Gifu, Gifu 501-1193, Japan email: yagasaki@cc.gifu-u.ac.jp June 22, 1999