Title used before an adult woman's name or surname, especially when it is not desired or possible to indicate her marital status with Miss or Mrs.
lowercase letters ... form the plural with an apostrophe and an s". The Oxford Style Manual on page 116 advocates the use of common sense.
How often have the words Ms and lowercase letters ... form the plural with an apostrophe and an s". The Oxford Style Manual on page 116 advocates the use of common sense. occurred in a corpus of books? (source: Google Ngram Viewer )