Available in unpaginated HTML, plain text (us-ascii), & Plucker formats from Ebook #22966.
Produced from Analog, April 1962. The HTML edition includes artwork credited to Brey from that issue. (The story title is also presented as an illustration of toy blocks; in the magazine edition, this appears to be a photograph, & the illustration credit is not with it at the head of the story.)
The Project Gutenberg wrapper identifies the author as Henry Maxwell Dempsey, but the text itself as Harry Harrison.
"Produced by Greg Weeks, Stephen Blundell and the Online Distributed Proofreading Team at http://www.pgdp.net".