1. Severinghaus JW, Astrup PB. History of blood gas analysis. J Clin Monit 1986;2:174–189
2. Merrick EB, Hayes, TJ. Continuous noninvasive measurement of arterial blood oxygen levels. Waltham, MA: Hewlett-Packard, 1976
3. Saunders NA, Powles ACP, Rebuck AS. Ear oximetry: accuracy and practicability in the assessment of arterial oxygenation. Am Rev Respir Dis 1976;114:745–748.
4. Cissick JH, Yockey CC, Byrd RD. Evaluation of the Hewlett-Packard ear oximeter for use during routine air transport of patients. Aviat Space Environ Med 1981;May:312–314
5. Douglas NJ, Brash HM, Wraith PK, et al. Accuracy, sensitivity to carboxyhemoglobin, and speed of response of the Hewlett-Packard 47201 ear oximeter. Am Rev Respir Dis 1979;119:311–313