According to {HEAD ~ principles} of {TAIL ~ the invention}, an educational device is provided for investigating and teaching about electromagnetic fields 
of
According to { HEAD ~ principles } of { TAIL ~ the invention } , an educational device is provided for investigating and teaching about electromagnetic fields
OTH OTH 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