  Free field equations, with various spins, for space-time algebras with
second-rank tensor (instead of usual vector) momentum are constructed. Similar
algebras are appearing in superstring/M theories. The most attention is payed
to the gauge invariance properties, particularly the spin two equations with
gauge invariance are constructed for dimensions 2+2 and 2+4 and connection to
Einstein equation and diffeomorphism invariance is established.
