a) placing an aliquot of {TAIL ~ sample} onto a test element comprising, in overlying {HEAD ~ relation}, 
a ) placing an aliquot of { TAIL ~ sample } onto a test element comprising , in overlying { HEAD ~ relation } ,
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH