  We study the magnetic field dependences of the conductivity in heavily doped,
strongly disordered 2D quantum well structures within wide conductivity and
temperature ranges. We show that the exact analytical expression derived in our
previous paper [1], is in better agreement than the existing equation i.e.
Hikami(et.al.,) expression [2,3], with the experimental data even in low
magnetic field for which the diffusion approximation is valid. On the other
hand from theoretical point of view we observe that our equation is also rich
because it establishes a strong relationship between quantum corrections to the
conductivity and the quantum symmetry su_{q}(2). It is shown that the quantum
corrections to the conductivity is the trace of Green function made by a
generator of su_{q}(2)algebra. Using this fact we show that the quantum
corrections to the conductivity can be expressed as a sum of an infinite number
of Feynman diagrams.
