Deletion of Maintenance-free operating period

Comment: The nomination provides no reason to delete.  If a source is wanted then this is done by adding one per  and , not by deleting anything.  And note that  only requires sources for controversial facts.  What is controversial here?  It's easy work to find an example such as ''https://books.google.co.uk/books?id=hsDLD3UHrGgC&pg=PA390 this
Stance: keep
Cited policy: Wikipedia:Editing policy (WP:IMPERFECT||WP:SOFIXIT||WP:V)