def pdf_Rosin_Rammler(d, k, m):
    r'''Calculates the probability density of a particle
    distribution following the Rosin-Rammler (RR) model given a 
    particle diameter `d`, and the two parameters `k` and `m`.
    
    .. math::
        q(d) = k m d^{(m-1)} \exp(- k d^{m})
        
    Parameters
    ----------
    d : float
        Specified particle diameter, [m]
    k : float
        Parameter in the model, [(1/m)^m]
    m : float
        Parameter in the model, [-]

    Returns
    -------
    pdf : float
        RR probability density function, [-]

    Notes
    -----

    Examples
    --------
    >>> pdf_Rosin_Rammler(1E-3, 200, 2)
    0.3999200079994667

    References
    ----------
    .. [1] Rosin, P. "The Laws Governing the Fineness of Powdered Coal." J. 
       Inst. Fuel. 7 (1933): 29-36.
    .. [2] Bayat, Hossein, Mostafa Rastgo, Moharram Mansouri Zadeh, and Harry 
       Vereecken. "Particle Size Distribution Models, Their Characteristics and
       Fitting Capability." Journal of Hydrology 529 (October 1, 2015): 872-89.
    '''
    return d**(m - 1.0)*k*m*exp(-d**m*k)