I adopt the Schouten (1954) kernel-index convention for symbols: Any addition to the symbol for a geometrical object
placed to the left of the symbol denotes a different object of the same geometric type; while any addition placed to the right
denotes the same object in a different coordinate system. Thus, if denotes a point of a differentiable manifold,
denotes a different point of the same manifold, while denotes the same point in a different coordinate
system.