A holder for securely positioning a sensor on a protruding part of a human body, {HEAD ~ which sensor} includes a light source transmitter and {TAIL ~ a receiver} sensitive to radiation emitted by the transmitter, comprising: 
includes
A holder for securely positioning a sensor on a protruding part of a human body , { HEAD ~ which sensor } includes a light source transmitter and { TAIL ~ a receiver } sensitive to radiation emitted by the transmitter , comprising :
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