Paper does not exist

RETRIEVAL OF PUBLISHED MATERIAL SUBJECT TO COPYRIGHT CONSTRAINTS

IMPORTANT NOTICE
This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.

COPYRIGHTED WORK
This work is protected under Copyright laws and its dissemination and distribution must abide by the general principles protecting Intellectual Property Rights. This work is archived at INESC Porto because one of the authors is or has been a researcher in this institution. Its Copyright may have been transferred to a third party. Nevertheless, authors usually retain the right to distribute copies for non-profit use by colleagues for research purpose. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the owner of the Copyright.

No paper available for download