by P. G. Ciarlet ; Notes by S. Kesavan. Lectures delivered at the Indian Institute of Science, Bangalore under the T. I. F. R. -I. I. Sc. Programme in Applications of Mathematics. Published for the Tata Institute of Fundamental Research, Bombay. -- Springer-Verlag, 1983. -- (Tata Institute of Fundamental Research lectures on mathematics and physics ; 71).