Cofecha is a commonly used free program for crossdating and measurement quality control. It is developed by Tree-Ring Lab and available at their web page. Outputs from Cofecha is normally found in the info files related to most of the dendro data files available at ITRDB. It runs under (at least) OSX and WindowsXP. It is a part of The Dendrochronology Program Library. It works with Tucson-formated dendro data files.