The room air filter apparatus of {HEAD ~ the present invention} has {TAIL ~ the advantages} of being easily and inexpensively constructed and operated 
The room air filter apparatus of { HEAD ~ the present invention } has { TAIL ~ the advantages } of being easily and inexpensively constructed and operated
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH