The current source provides constant currents IR1 and IR2 through {HEAD ~ resistors R1} and {TAIL ~ R2}, respectively 
The current source provides constant currents IR1 and IR2 through { HEAD ~ resistors R1 } and { TAIL ~ R2 } , respectively
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH