Erratum

Unfortunately, a mistake (in the catchlines) was made in the publisher's office before the issue was sent for printing. Two title pages were switched. Page 765 should be page 777, the title page of the Liu paper, and page 777 should be 765, the title page of the Takahashi paper.

We deeply regret this error and apologise to the authors: Yasutake Takahashi, Rieko Iida and Tsutomu Miyashi; Lan Liu, Robert B. Pansu, Jean Faure, Jacques Roncin, Bernard Arrio and Rene Lapouyade; and to the Guest Editor, Hirochika Sakuragi, for the inconvenience caused.