What's strange is that I have a copy of the MLA Handbook (8th ed.) and I can't locate any specific guidance on how to handle multiple locations. It only mentions how to reference a single page or a single range of pages.
However, Simon Fraser University's MLA Citation Guide may give an indirect example:
At the end of your paper, you will list all your sources on a separate page entitled Works Cited (pp. 20-54; pp. 102-116).
Now, that is actually referencing page numbers of the MLA Handbook itself, but if the nomenclature it's using is in an acceptable MLA format, then your own Works Cited entry would likely look the same:
pp. 10-11; p. 15; p. 19
I can't imagine that reasonable guidance would say to provide a separate entry in Works Cited for each identical source but different location.
Also note that the use of the plus sign is reserved for periodicals:
2.5.1 PLUS SIGN WITH PAGE NUMBER
If a work in a periodical (journal, magazine, newspaper) is not printed on consecutive pages, include only the first page number and a plus sign, leaving no intervening space.