classical theory of calculus of valuationsclassical theory of calculus of variationsclassificationclassification problemclassification procedureclassification theoremclassificatory procedureclassified dataclassifyclauseclawclearclearanceclearance angleclearing of fractionscleavageclerical serviceclerkclienteleclifford algebraclifford angebraclifford groupclifford numbersclipclippedclipped functionclockwiseclockwise rotationclockworkcloseclose a bracketclose accuracyclosedclosed and open setclosed ballclosed broken lineclosed cardclosed contourclosed convex curveclosed convex surfaceclosed currentclosed curveclosed discclosed formclosed graph theoremclosed groupclosed half spaceclosed intervalclosed lineclosed linear subspace