The Author-Page style of in-text referencing (e.g., MLA) is the default for all students in all subjects, however, for the IB Diploma programme, some departments choose a different style -- whether in-text Author-Date-Page (e.g., APA) or bottom-of-the-page Footnotes (e.g., Chicago) -- as indicated below.
This is the style with "author" -- and "page number" (if relevant).
Scentists have proved that mice can sing (Mice Research). But others disagree (Smith, Brown, and Kaser 135).
This is the style with "author" and "date" -- and "page number" (if relevant). For example:
Scientists have proved that mice can sing ("Mice Research," 2012). But others disagree (Smith, Brown, & Kaser, 2013, p. 135).
This is the "foonotes" style.
Scientists have proved that mice can sing.1 But others disgree.2
1. "Mice Research," Scientists United, 2012, accessed September 1, 2014, http://sciunited.com/miceresearch.
2. Anne Smith, Nancy Brown, and Kate Kaser, Research on Mice and Music (London: Oxford University Press, 2013), 135.
NOTE: All three of the styles above would still have a "Works Cited" or "Bibliography" section at the end of the paper, where all the sources are listed alphabetically, in one list.