I've updated my 14 May entry on Donald Keith's Time Machine stories, since Google Books has acquired more scans.

At this point, I believe I have links to every Time Machine story appearing in Boys' Life. If you know of any others, please inform me.

I put a partial list of the stories into Wikipedia's Donald Keith entry a while ago. It will need to be updated. I thought it would be nice if the series had its own article, so I started one, though my Wikipedian skills are minimal.