00358nam a2200121Ia 4500082002000000100001800020245007600038260004800114300002100162490004300183500000500226700000500231  a530.3bSe516.MM  aSewell, M. J.  aMaximum and minimum principles; a unified approach, with applicationsb  aCambridgebCambridge University Pressc1987  axvi, 468p. Index  aCambridge texts in Applied Mathematics  a  a