2022] TRAN™ Pulse Oximeter, AS Used in The NHS, Oxygen Monitor Finger Adults, Pulse Oximeter NHS Approved, Oximeter NHS Approved UK, with Additional TRAN Oxygen Guide™ from NHS Doctors : Amazon.co.uk: Health
Covid: How a £20 gadget could save lives - BBC News
Design of Pulse Oximeters - 1st Edition - John G. Webster - Routledge