{HEAD ~ A light source} 14 wherein said helical portion turns through an angle of {TAIL ~ at least about 720°} 
{ HEAD ~ A light source } 14 wherein said helical portion turns through an angle of { TAIL ~ at least about 720 ° }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL