Would you be so kind as to send me a pointer to this paper? Thanks. Lorenz Lorenz Huelsbergen Rm. 2C-307 AT&T Bell Laboratories 600 Mountain Ave. Murray Hill, NJ 07974 phone: 908 582 4628 fax: 908 582 4981 or 908 582 7550 e-mail: lorenz@research.att.com