One must "form the possessive singular of nouns by adding 's," even if the last letter in the word is S; therefore, it's Harris's book, not Harris' book. Was Mr. Strunk being pedantic? I have to admit, I am a bit reluctant to add 's to words ending with the letter S, so now I'm doing my best to avoid writing them at all. I know, however, that it's not right to avoid the problem... Can anybody help me out?
You are talking about Synthetical Genitive.
This Genitive is formed as follows:
1. singular+'s
eg. My mother's blouse
The teacher's desk
2. plural noun+'
eg. The boys' ball
The parents' bedroom
3. irregular plural nouns+'s
eg The women's society
The children's toys
4. Proper nouns ending in -s usually get only the apostrophe, although 's may also be used, in either case the ending of the noun being normally pronounced /iz/
I have seen people say that the 's' should be added for last names and foreign names, so there are different views on the issue. I use it in names where it is an accepted form (St James's Park), but I would say "Dickens' novels".
So would I be right in saying that it's okay either way? Perhaps, since people seem to be divided on this issue, I should just go with popular usage and reserve using my s's for the accepted forms. Hmm...good advice, good advice.
according to William Strunk Jr. 
Linear Mode
