Capitalize all major words in the title of a book, periodical, film, video, and TV show when it is mentioned in the text. The following are not considered major words: conjunctions, articles, and short prepositions. However, capitalize all words of four letters or more. Titles should also be italicized.
The Element of Style
In their book How Children Develop (2010)…
(American Psychological Association, 2010, pp. 101-102, 104-105)