Goodreads Librarians Group discussion

Is there a particular website that Goodreads uses as a rule/guide for capitalization? I've tried searching endlessly through discussion topics and Google. The Librarian Manual only says "The title should be capitalized according to standard title capitalization for the language of the edition" but does not reference a particular website as a guide. I know to not capitalize prepositions with four letters or less and coordinating conjunctions but what is the rule on subordinating conjunctions? I've Googled "English standard title capitalization" and one website suggested capitalizing subordinating conjunctions but I've seen corrections made by another librarian that changed "when" to lower case in the middle of a book title. I don't want to undo another librarian's edit if it is indeed correct to lower case it.

This is the website where I found this reference: http://grammar.yourdictionary.com/cap...

Thank you!
Rhonda L.

If I am not mistaken you only capitalize in English the content words: nouns, verbs, adjectives and adverbs; so you don't capitalize prepositions, articles or conjunctions.

Usually I capitalize the title as it's printed on the cover, unless the cover has all caps or all lowercase. This is especially true for non-English titles where I don't have a clue what the capitalization rules are.

I found a site that, so far, seems to correctly capitalize titles.

http://titlecapitalization.com/