def diffusivity_Gu1997(c_e):
    """
    Dimensional Fickian diffusivity of sulfuric acid [m2.s-1], from [1]_ citing [2]_
    and agreeing with data in [3]_, as a function of the electrolyte concentration
    c_e [mol.m-3].

    References
    ----------
    .. [1] WB Gu, CY Wang, and BY Liaw. Numerical modeling of coupled electrochemical
           and transport processes in lead-acid batteries. Journal of The
           Electrochemical Society, 144(6):2053–2061, 1997.
    .. [2] WH Tiedemann and J Newman. Battery design and optimization. Journal of
           Electrochemical Society, Softbound Proceeding Series, Princeton, New York,
           79(1):23, 1979.
    .. [3] TW Chapman and J Newman. Compilation of selected thermodynamic and transport
           properties of binary electrolytes in aqueous solution. Technical report,
           California Univ., Berkeley. Lawrence Radiation Lab., 1968.

    """
    return (1.75 + 0.00026 * c_e) * 1e-09
