The Chicago style (or Oxford style) uses footnotes in the text, and the source is reported in the footnote.

The footnote used in the text will look like this:

“Arnold Smith has studied this phenomenom at length.1“

The footnote at the bottom of the page will look like this:

1 Arnold Smith, Living together or apart: An Investigation of the Housing Preferences among College Students (New York: Harper & Lea Publishers, 1998), 82–83.

For subsequent mentions of the paper, on the same page or on other pages, the citation is shortened:

2 Smith, Living together or apart, 88.