Here, {HEAD ~ equation} denotes {TAIL ~ the spherical surface} when K=A=B=C=0 
Here , { HEAD ~ equation } denotes { TAIL ~ the spherical surface } when K = A = B = C=0
OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH