Online Writing Lab at Purdue University
Purdue University Owl: Using Hyphens
Do you know when to use hyphens? Here's a resource that lists when to use hyphens in adjectives, in compound numbers, after prefixes, and in between line breaks with examples of each.
Grammarly
Grammarly Blog: Hyphen in Compound Numbers
Rules and examples for using a hyphen when writing compound numbers. L.11-12.2a Hyphens
Other
Exploring English: Hyphen Rules
This site contains a brief outline of the uses of the hyphen and provides examples.