Robert Jäschke, Andreas Hotho, Christoph Schmitz, Bernhard Ganter, und Gerd Stumme. Discovering shared conceptualizations in folksonomies. Web Semant., (6)1:38--53, Elsevier Science Publishers B. V., Amsterdam, The Netherlands, The Netherlands, 2008. [PUMA: concept formal trias analysis fca ontologyhandbook myown] URL