Pubmed IDs apparently start at 1:
However, we currently only recognise a pubmed id if it is 6 or 7 digits long. We should expand the definition in
CitoidService.prototype.addResponseFunction (https://github.com/wikimedia/citoid/blob/master/lib/CitoidService.js) to include these.
In order to get citoid working on your computer, you'll need to download both Node version 10.0 (for citoid) and xpcshell version 29.0 (for Zotero) to get both of them working. There are installation instructions and more information available at https://www.mediawiki.org/wiki/Citoid
(For this task, you don't strictly need to install Zotero, but the tests will fail without it installed, so you will need to install it to create the tests.)