S` or`s

1. Plural nouns not ending in 's' take both the apostrophe and the 's':
"The children's toys."
"The men's cars."

2. Nouns that take -s for the plural add only the apostrophe to indicate possession (this is called 'zero genitive'):
"The boys' toys."
"The dogs' tails."

3. The 'zero form' is also used:
a. with Greek names of more than one syllable:
"

In the case of Burns and Dickens, it is also perfectly correct to add 's, according to some grammarians.

I'm not taking sides here, but this makes the rule much simpler. (I used to teach English in Spain, and believe me, my students always appreciated anything that would simplify things for them!)

I agree with Boston . Its hard to follow a response of an expert who uses too much difficult words than who better prefer to be simple in writting.

Atesttaker,
I hope you don't mean *** am the expert? I'm only a teacher.

I'm sorry you find the rules confusing or difficult to understand, but you'll find the same rules in any fairly good grammar book. I didn't make them up. I had to study these rules too, in order to speak/write "educated" English. And I think it was worth both the time and the effort.