USEARCH documentation for older releases 

Version 6 and later manuals (web pages)
/usearch/manual6
/usearch/manual7
/usearch/manual8.0
/usearch/manual8.1

Older manuals (PDF format)
Version 1.1
Version 2.0
Version 2.1
Version 3.0
Version 4.0
Version 4.1
Version 4.2
Version 5.0
Version 5.1
Version 5.2