In order to install on line documentation and help, although there are alternatives, preferred way is (on a PC with Windows-95) as follows: * Put the file InvariantsSymmetries.m into C:\Program Files\Wolfram Research\Mathematica\ 4.0\AddOns\Applications\Integrability * Put the file init.m into C:\Program Files\Wolfram Research\Mathematica\ 4.0\AddOns\Applications\Integrability\Kernel * Put the files BrowserCategories.m, IntegrabilityPalettes.nb, and Documentation.nb into C:\Program Files\Wolfram Research\Mathematica\ 4.0\AddOns\Applications\Integrability\Documentation\English * Start Mathematica 4.0, Select "Help" from the main menu, and then select "Rebuild Help Index" (done only once for every addition to the system). Then choose "Add-ons" under the "Find in Help" item and you will see the item "Integrability" listed there. On other systems put the corresponding files into appropriate places under AddOns directory. * In any Mathematica notebook you can read in the package via the Needs["Integrability`InvariantsSymmetries`"] command and learn about the functions via e.g. ??PDEInvariants