def uv76_to_xy(u76, v76):       # CIE1976 to CIE1931
    """ convert CIE1976 u'v' to CIE1931 xy coordinates
    :param u76: u' value (CIE1976)
    :param v76: v' value (CIE1976)
    :return: CIE1931 x, y """
    denominator = (((9 * u76) / 2) - (12 * v76) + 9)
    
    if denominator == 0.0:
        x, y = 0.0, 0.0
    else:
        x = ((27 * u76) / 4) / denominator
        y = (3 * v76) / denominator

    return x, y     # CIE1931 x, y