text: These attachments are part of the present package. Attachment1.pdf is simply a statement of PNAS procedure. Note that members of the NAS are permitted to communicate up to 4 papers per year. The members are responsible for obtaining two reviews of their own papers and to report the reviews and their responses to the reviews. Note, as well, that rejection of such contributions by the Board of PNAS is a rare event, involving approximately 2% of all contributions.