1. Dorsch JA, Dorsch SE. Understanding anesthesia equipment. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2007. p. 108–10.
2. ASTM (American Society for Testing and Materials) Standard F1850-00, clause 51.13.1 Protection Against Accidental Delivery of Hypoxic Gas Mixtures.
3. International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) Standard EN60601-2-13, clause 51.102.2 Anaesthetic gas delivery system.
4. De Cooman S, Schollaert C, Hendrickx JF, Peyton PJ, Van Zundert T, De Wolf AM. Hypoxic guard systems do not prevent rapid hypoxic inspired mixture formation. J Clin Monit Comput. 2014 Oct 1, published ahead of print.
5. User’s Manual FLOW-i 4.0 Anesthesia System, Infologic 1.58. Maquet Getinge group, p. 66–7.