Cita APA (7th ed.)

Cowen, P., Parry-Billings, M., & Newsholme, E. (1989). Decreased plasma tryptophan levels in major depression.

Cita Chicago (17th ed.)

Cowen, P., M. Parry-Billings, i E. Newsholme. Decreased Plasma Tryptophan Levels in Major Depression. 1989.

Cita MLA (9th ed.)

Cowen, P., et al. Decreased Plasma Tryptophan Levels in Major Depression. 1989.