def _Sublimation_Pressure(T):
    """Sublimation Pressure correlation

    Parameters
    ----------
    T : float
        Temperature, [K]

    Returns
    -------
    P : float
        Pressure at sublimation line, [MPa]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 50 ≤ T ≤ 273.16

    Examples
    --------
    >>> _Sublimation_Pressure(230)
    8.947352740189152e-06

    References
    ----------
    IAPWS, Revised Release on the Pressure along the Melting and Sublimation
    Curves of Ordinary Water Substance, http://iapws.org/relguide/MeltSub.html.
    """
    if 50 <= T <= 273.16:
        Tita = T/Tt
        suma = 0
        a = [-0.212144006e2, 0.273203819e2, -0.61059813e1]
        expo = [0.333333333e-2, 1.20666667, 1.70333333]
        for ai, expi in zip(a, expo):
            suma += ai*Tita**expi
        return exp(suma/Tita)*Pt
    else:
        raise NotImplementedError("Incoming out of bound")
Sublimation Pressure correlation

    Parameters
    ----------
    T : float
        Temperature, [K]

    Returns
    -------
    P : float
        Pressure at sublimation line, [MPa]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 50 ≤ T ≤ 273.16

    Examples
    --------
    >>> _Sublimation_Pressure(230)
    8.947352740189152e-06

    References
    ----------
    IAPWS, Revised Release on the Pressure along the Melting and Sublimation
    Curves of Ordinary Water Substance, http://iapws.org/relguide/MeltSub.html.