Final answer:
The correct punctuation mark to separate multiple works in a single parenthetical reference is a semicolon. This aligns with MLA style guidelines for proper citation in academic writing. A corresponding entry for each citation must also be made on the Works Cited page to avoid plagiarism.
Step-by-step explanation:
When including two or more works within a single parenthetical reference, the appropriate punctuation mark to use is a semicolon. For instance, in the MLA style, separate citations should be formatted by citing each work as you normally would and using semicolons to separate them. Examples can be seen in literature citations: for prose works, additional information such as chapter or scene might follow the page number and be separated by a semicolon as well (78; act 2). Similarly, when referencing different authors within the same in-text citation, the semicolon comes into play: (Garrison 57; Mechling and Mechling 109).
Remember that every parenthetical citation should point the reader to a detailed entry on the Works Cited page. This ensures that the source can be easily found by the reader, avoiding any form of plagiarism. The Works Cited entry must match the in-text citation to maintain the integrity of your writing and provide clear references for your sources.