Subsequent citations of sources already given in full should be shortened whenever possible. The short form should include enough information to remind readers of the full title or to lead them to the appropriate entry in the bibliography. The most common short form consists of the last name of the author and the main title of the work cited, usually shortened if more than four words.
Full footnote:
1 Samuel A. Morley, Poverty and Inequality in Latin America: The Impact of Adjustment and Recovery (Baltimore: Johns Hopkins University Press, 1995), 24–25.
Subsequent citation:
Morley, Poverty and Inequality, 43.
Footnote:
23 Paul Jackson, Cut and Fold Paper Textures (London: Laurence King, 2017), 36; Jason Franz, "Magic Wand: The Power of the Ballpoint Pen," Drawing 14, no. 54 (Summer 2017), Art & Architecture Complete.
Bibliography entry:
Franz, Jason. "Magic Wand: The Power of the Ballpoint Pen," Drawing 14, no. 54 (Summer 2017), Art & Architecture Complete.
Jackson, Paul. Cut and Fold Paper Textures (London: Laurence King, 2017).
Example:
Shakespeare, Julius Caesar, act 3, sc. 1. Caesar’s claim of constancy should be taken with a grain of salt.
Example:
23 Louis Zukofsky, “Sincerity and Objectification,” Poetry 37 (February 1931): 269, quoted in Bonnie Costello, Marianne Moore: Imaginary Possessions (Cambridge, MA: Harvard University Press, 1981), 78.
Chicago Manual of Style 17th edition discourages the use of ibid. in your footnotes in favor of shortened citations. Shortened citations generally take up less than a line, meaning that ibid. saves no space.