def chen_celikovsky(XYZ, t, a=36, b=3, d=20):
    """
    The Chen-Celikovsky Attractor.
    x0 = (0.1,0.1,0.1)
    """
    x, y, z = XYZ
    x_dt = a * (y - x)
    y_dt = -x * z + d * y
    z_dt = x * y - b * z
    return x_dt, y_dt, z_dt