R.C. Heel, R.N. Brogden, T.M. Speight, G.S. Avery. Penbutolol: a preliminary review of its pharmacological properties and therapeutic efficacy in hypertension and angina pectoris. „Drugs”. 22 (1), s. 1–25, 1981. DOI: 10.2165/00003495-198122010-00001. PMID: 7261952.
R.C. Heel, R.N. Brogden, T.M. Speight, G.S. Avery. Penbutolol: a preliminary review of its pharmacological properties and therapeutic efficacy in hypertension and angina pectoris. „Drugs”. 22 (1), s. 1–25, 1981. DOI: 10.2165/00003495-198122010-00001. PMID: 7261952.