def trans_coeff(eq, x, y, z):
    """This function is provided by MOKA2 Development Team (1996.xx.xx)
    and used in SOSS system."""
    tt = (eq - 2000.0) / 100.0

    zeta = 2306.2181 * tt + 0.30188 * tt * tt + 0.017998 * tt * tt * tt
    zetto = 2306.2181 * tt + 1.09468 * tt * tt + 0.018203 * tt * tt * tt
    theta = 2004.3109 * tt - 0.42665 * tt * tt - 0.041833 * tt * tt * tt

    zeta = math.radians(zeta) / 3600.0
    zetto = math.radians(zetto) / 3600.0
    theta = math.radians(theta) / 3600.0

    p11 = (math.cos(zeta) * math.cos(theta) * math.cos(zetto) -
           math.sin(zeta) * math.sin(zetto))
    p12 = (-math.sin(zeta) * math.cos(theta) * math.cos(zetto) -
           math.cos(zeta) * math.sin(zetto))
    p13 = -math.sin(theta) * math.cos(zetto)
    p21 = (math.cos(zeta) * math.cos(theta) * math.sin(zetto) +
           math.sin(zeta) * math.cos(zetto))
    p22 = (-math.sin(zeta) * math.cos(theta) * math.sin(zetto) +
           math.cos(zeta) * math.cos(zetto))
    p23 = -math.sin(theta) * math.sin(zetto)
    p31 = math.cos(zeta) * math.sin(theta)
    p32 = -math.sin(zeta) * math.sin(theta)
    p33 = math.cos(theta)

    return (p11, p12, p13, p21, p22, p23, p31, p32, p33)