English: pluralize 'vowel+o' ending as 'vowel+o+s'

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See:

• The Cambridge Grammar of the English Language (p. 1586, The alternation between ·s and ·es)
• http://english.stackexchange.com/questions/23229/is-there-a-good-rule-of-thumb-for-plurals-from-words-ending-in-o
• http://www.oxforddictionaries.com/us/words/plurals-of-nouns