This is the third volume (out of four total) of the Special Issues for celebrating the seventieth birthday of Neil Trudinger.

Sun-Yung Alice Chang, Department of Mathematics, Princeton University, U. S. A.

Nicola Fusco, Dipartimento di Matematica “R. Caccioppoli",, Universita di Napoli "Federico II", Italy

Tai-Ping Liu, Institute of Mathematics, Academia Sinica, Taiwan, and Department of Mathematics, Stanford University, U.S.A. .

Alan McIntosh, Centre for Mathematics and its Applications, Mathematical Sciences Institute, Australian National University, Australia