While abbreviations are rare in academic prose, they are perfectly common in citations.
Abbreviations that consist mostly of capital letters don’t need periods or spaces:
However, for people’s initials you can add periods and spaces unless the entire name is abbreviated:
C. S. Lewis
R. A. Shoaf
You’ll find though that the spaces between initials are often omitted, as anyone researching G.I. Joe would soon discover.
Lowercase abbreviations usually end in periods:
Lowercase abbreviations of multiple words may contain extra periods:
This rule does not apply universally. An exception would be mph (miles per hour), which does not need extra periods.
Any months longer than four letters can be abbreviated:
Here’s a list of other abbreviations used in MLA citations:
ch. = chapter
dept. = department
ed. = edition
e.g. = for example (from the Latin exempli gratia)
et al. = and others (from the Latin et alii)
etc. = and so forth (from the Latin et cetera)
i.e. = that is (from the Latin id est)
no. = number
P = Press
p. = page
pp. = pages
par. = paragraph
qtd. in = quoted in
rev. = revised
sec. = section
trans. = translation
U = University
UP = University Press
vol. = volume
For more information on abbreviations, see Appendix 1 of the MLA Handbook (9th ed.).