When PMC was acquired by the MUSE project at John Hopkins Press, the article ceased to be available to the general public (only those people who subscribe or whose libraries subscribe to MUSE or to PMC had access to issues of PMC prior to the current one). Believing that PMC's policy of allowing free access to its articles was one of its strong points, I reposted the article here. (My contract with PMC, which reassigns ownership of the article to me, clearly allowed me to do this.)
After much public discussion, the editors of PMC and MUSE decided to make text-only versions of back issues available to non-subscribers. Full editions, with appropriate HTML bells and whistles, are available to subscribers. Although this decision is not without some adverse consequences (texts which do not lend themselves to text-only presentation are still available only to subscribers), for articles like my own it was an intelligent compromise. I applaud their decision, and recommend that you show support for online scholarly publishing in any way possible.
I am still maintaining the article on this site, however, because there are links to this version on search engines and indexes such as the Voice of the Shuttle page.