def Zuo_Stenby(T, Tc, Pc, omega):
Tc_1, Pc_1, omega_1 = <NUM_LIT>, <NUM_LIT>/<NUM_LIT>, <NUM_LIT><EOL>Tc_2, Pc_2, omega_2 = <NUM_LIT>, <NUM_LIT>/<NUM_LIT>, <NUM_LIT><EOL>Pc = Pc/<NUM_LIT><EOL>def ST_r(ST, Tc, Pc):<EOL><INDENT>return log(<NUM_LIT:1> + ST/(Tc**(<NUM_LIT:1>/<NUM_LIT>)*Pc**(<NUM_LIT:2>/<NUM_LIT>)))<EOL><DEDENT>ST_1 = <NUM_LIT>*(<NUM_LIT:1> - T/Tc)**<NUM_LIT>  <EOL>ST_2 = <NUM_LIT>*(<NUM_LIT:1> - T/Tc)**<NUM_LIT>  <EOL>ST_r_1, ST_r_2 = ST_r(ST_1, Tc_1, Pc_1), ST_r(ST_2, Tc_2, Pc_2)<EOL>sigma_r = ST_r_1 + (omega-omega_1)/(omega_2 - omega_1)*(ST_r_2-ST_r_1)<EOL>sigma = Tc**(<NUM_LIT:1>/<NUM_LIT>)*Pc**(<NUM_LIT:2>/<NUM_LIT>)*(exp(sigma_r)-<NUM_LIT:1>)<EOL>sigma = sigma/<NUM_LIT:1000>  <EOL>return sigma<EOL>
r'''Calculates air-water surface tension using the reference fluids
    methods of [1]_.

    .. math::
        \sigma^{(1)} = 40.520(1-T_r)^{1.287}
        \sigma^{(2)} = 52.095(1-T_r)^{1.21548}
        \sigma_r = \sigma_r^{(1)}+ \frac{\omega - \omega^{(1)}}
        {\omega^{(2)}-\omega^{(1)}} (\sigma_r^{(2)}-\sigma_r^{(1)})
        \sigma = T_c^{1/3}P_c^{2/3}[\exp{(\sigma_r)} -1]

    Parameters
    ----------
    T : float
        Temperature of fluid [K]
    Tc : float
        Critical temperature of fluid [K]
    Pc : float
        Critical pressure of fluid [Pa]
    omega : float
        Acentric factor for fluid, [-]

    Returns
    -------
    sigma : float
        Liquid surface tension, N/m

    Notes
    -----
    Presently untested. Have not personally checked the sources.
    I strongly believe it is broken.
    The reference values for methane and n-octane are from the DIPPR database.

    Examples
    --------
    Chlorobenzene

    >>> Zuo_Stenby(293., 633.0, 4530000.0, 0.249)
    0.03345569011871088

    References
    ----------
    .. [1] Zuo, You-Xiang, and Erling H. Stenby. "Corresponding-States and
       Parachor Models for the Calculation of Interfacial Tensions." The
       Canadian Journal of Chemical Engineering 75, no. 6 (December 1, 1997):
       1130-37. doi:10.1002/cjce.5450750617