Gérard Kientega Ivo Rosenberg Metric Properties of Tolerances. 209-218 2010 16 Multiple-Valued Logic and Soft Computing 1-2 http://www.oldcitypublishing.com/MVLSC/MVLSCabstracts/MVLSC16.1-2abstracts/MVLSCv16n1-2p209-218Kientega.html db/journals/mvl/mvl16.html#KientegaR10