Many people are concerned about standards in written English and have produced similar websites, and all credit to them. I think all though adopt what I think is a confusing multi-rule approach. I hope you can see that the consistent one rule approach adopted on this site fits all the examples given on other sites.
The Apostrophe Protection Society
The Owl online Writing Lab (archive)
Taming the Apostrophe!
The Apostrophe - Ottawa University
Punctuation Made Simple - still not simple enough though.
Sharon Colon's Apostrophe Page - some nice pictures of straying apostrophes
Literacy Education Online
Queen's English Society
Problems with apostrophes - Paul Doherty's take on this.
The apostrophe: where to stick it
There are many more - just Google "Apostrophe". But they all insist on you learning at least two separate rules. But you know now there's really only one.
World Wide Words - a fascinating compendium of linguistic lore which one can browse for far too long!
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