a4.1. Names ending in -s require only an apostrophe to denote possession. Names ending in -x or -z require -'s (Jesse Helms' amendment, Samantha Fox's video, Richard Rodriguez's essay).
a4.2. Plural nouns not ending in -s add -'s (women's rights; alumni's donations); plural nouns ending in -s add only an apostrophe (Romanians' struggle; squirrels' nest).
a4.3. Singular common nouns ending in -s add -'s (actress's role, boss's tyranny) except when the noun following begins with an s- (actress' spark, boss' signature).
a4.4. Acronyms require an apostrophe and -s for possessive form. (The RA's job is to be a leader.)
a4.5. Avoid constructions that involve making an inanimate
object possessive, especially when the object of possession is abstract.
"The business's failure" is better expressed as "The failure
of the business"; likewise "chemistry's rules" should be
"the rules of chemistry."
Exception: References to specific nations or corporations
can usually take possessive form, primarily because they are considered
animate in both legal and literary contexts.
Exception: Familiar phrases in which the object of possession is
concrete and uniquely applicable to the possessor are
acceptable (car's transmission, department's budget, ship's wake).
Exception: Anthropomorphic uses of "life," "death"
or forces of nature may use possessive forms (life's mortal coil, death's
call, storm's fury, wind's murmur).
a4.6. In constructions involving joint possession, use an apostrophe only after the last possessor (Donald and Ivana's marriage crumbled). Use an apostrophe after both names if the object(s) possessed belongs to each (Donald's and Ivana's claims in The Enquirer).
a4.7. Its as a possessive takes no apostrophe; it's as a contraction takes an apostrophe (The college insulted its constituencies; it's a cruel, cruel summer).