One author may frequently reference (cite) another author, particularly in articles and books. These are called secondary sources. Citing these secondary sources can be somewhat convoluted.
The 11th edition of the AMA Manual of Style doesn't specifically discuss secondary citations, though it was mentioned in the 10th edition which suggested giving the citation for the original source, followed by “Cited by” or “Quoted by” and the secondary source details. You must distinguish between citation and quotation (ie, between work mentioned and words actually quoted). In the text, the name of the original author, rather than the secondary source, should be mentioned.
Whenever possible, go find the full citation for the secondary source and then cite that source in your paper (you may find other material you can use as well.) However, only sources actually consulted should be cited.