However, it has been found that {HEAD ~ the currently preferred approach} is to use {TAIL ~ a multipole} focusing magnetic or electrostatic field 
However , it has been found that { HEAD ~ the currently preferred approach } is to use { TAIL ~ a multipole } focusing magnetic or electrostatic field
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH