Effectively, there is no theoretical limit to {HEAD ~ the applicability} of {TAIL ~ the invention}, although practical difficulties may occur at extremes of low and high frequency 
Effectively , there is no theoretical limit to { HEAD ~ the applicability } of { TAIL ~ the invention } , although practical difficulties may occur at extremes of low and high frequency
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH