  We study electronic states of semi-infinite graphene with a corner edge,
focusing on the stability of edge localized states at zero energy. The
60{\deg}, 90{\deg}, 120{\deg} and 150{\deg} corner edges are examined. The
60{\deg} and 120{\deg} corner edges consist of two zigzag edges, while 90{\deg}
and 150{\deg} corner edges consist of one zigzag edge and one armchair edge. We
numerically obtain the local density of states (LDOS) on the basis of a
nearest-neighbor tight-binding model by using Haydock's recursion method. We
show that edge localized states appear along a zigzag edge of each corner edge
structure except for the 120{\deg} case. To provide insight into this behavior,
we analyze electronic states at zero energy within the framework of an
effective mass equation. The result of this analysis is consistent with the
behavior of the LDOS.
