Possessives

We’re actually going to follow the Chicago Manual (CMS15,  7.17): “The possessive of most singular nouns is formed by adding an apostrophe and an s, and the possessive of plural nouns (except for a few irregular plurals that do not end in s) by adding an apostrophe only.”

Kansas’s weather                                      the Lincolns' marriage
Burns’s poetry                                          dinner at the Browns' home         
Marx’s theories                                         the Martinezes' daughter         
Berlioz’s works
Strauss’s Vienna
Dickens’s novels

Exception (CM 7.20): “The possessive is formed without an additional s for a name of two or more syllables that ends in an eez sound.”

Euripides’ tragedies
the Ganges’ source
Xerxes’ armies