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Original work published on the Web is automatically copyrighted. Republished material requires permission from the current copyright holder. For material on this site, publishers requested their respective copyright statements be posted, and they are given below.

© Academic Press (http://www.apnet.com/) The article posted has been published in the Journal of Mathematical Analysis and Applications, the only definitive repository of the content of that article which has been certified and accepted after peer review. Copyright and all rights therein are retained by Academic Press. This material may not be copied or reposted without explicit permission. See also the International Digital Electronic Access Library at http://www.idealibrary.com or http://www.europe.idealibrary.com.

© Academic Press (http://www.ensmp.fr/aflb/)

© American Institute of Physics. (http://www.aip.org) Reprinted with permission from the journal cited.

© Birkhauser (http://www.Birkhauser.com/) Reprinted with permission of Birkhauser Press.

© Cambridge University Press (http://www.cup.cam.ac.uk/) Reprinted with permission of Cambridge University Press. All reproduction, copying or distribution of this material in any format, beyond single copying by an authorized individual for personal use, must first receive the written consent of Cambridge University Press.