Browse our directory of GPM data products (https://gpm.nasa.gov/data/directory) to locate your desired algorithm, then click on the links in the algorithm description under "Documentation". All documentation is also available at the Precipitation Processing System website (https://pps.gsfc.nasa.gov/). Note that "GPM data products" includes data from both the GPM and TRMM eras, uniformly processed using the most current GPM-based algorithms.