  We study the behavior of positive solutions of p-Laplacian type elliptic
equations of the form Q'(u) := -p-Laplacian(u) + V |u|^(p-2) u = 0 in Omega
near an isolated singular point zeta, where 1 < p < inf, Omega is a domain in
R^d with d > 1, and zeta = 0 or zeta = inf. We obtain removable singularity
theorems for positive solutions near zeta. In particular, using a new
three-spheres theorems for certain solutions of the above equation near zeta we
prove that if V belongs to a certain Kato class near zeta and p>d
(respectively, p<d), then any positive solution u of the equation Q'(u)=0 in a
punctured neighborhood of zeta=0 (respectively, zeta=inf) is in fact continuous
at zeta. Under further assumptions we find the asymptotic behavior of u near
zeta.
