This volume contains all papers presented at the workshop "Sequences '91: Methods in Communication, Security and Computer Science," which was held Monday, June 17, through Friday, June 21, 1991, at the Hotel Covo dei Saraceni, Positano,ltaly. The event was sponsored by the Dipartimento di Informatica ed Applicazioni of the University of Salerno and by the Dipartimento di Matematica of the University of Rome. We wish to express our warmest thanks to the members of the program Committee: Professor B. Bose, Professor S. Even, Professor Z. Galil, Professor A. Lempel, Professor J. Massey, Professor D. Perrin, and Professor J. Storer. Furthermore, Professor Luisa Gargano provided effective, ceaseless help both during the organization of the workshop and during the preparation of this vol- ume. Finally, we would like to express our sincere gratitude to all participants of the Workshop. R. M. C. A. D. S. U. V. Salerno, December 1991 Contents Preface...Vll Contributors...Xill Communication On the Enumeration of Dyadic Distributions I. F. Blake, GH. Freeman, and P. R. Stubley ...3 Detection of Skew in a Sequence of Subsets M. Blaum and J. Bruck ...12 Asymmetric Error Correcting Codes B. Bose and S. Cunningham ...24 Binary Perfect Weighted Coverings (PWC) GoO. Cohen, S. N. Litsyn, and H. F. Mattson, Jr...36 Read/Write Isolated Memory M. Cohn ...52 Polynomial-Time Construction of Linear Codes with Almost Equal Weights G. Lachaud and J. Stern ...59 Welch's Bound and Sequence Sets for Code-Division Multiple-Access Systems J. L. Massey and T. Mittelholzer ...