The student is quoting from page 96 of the book How to Have a Smarter Baby, written by Susan Ludington-Hoe and Susan K. Golant and published in 1985.

Ludington-Hoe (1985) noted that music “has been known to stimulate the brain’s right side (fostering creativity) and actually help babies gain more weight and cry less” (p. 96).

Ludington-Hoe and Golant (1985) noted that music “has been known to stimulate the brain’s right side (fostering creativity) and actually help babies gain more weight and cry less” (p. 96).

For a work with two authors, both authors should be named in the signal phrase.