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