'Stephens 1974, doesn\'t have p-value formula for A^2'

@cache_readonly
def asqu(self):

    nobs = self.nobs
    cdfvals = self.cdfvals
    asqu = (((- (((2.0 * np.arange(1.0, (nobs + 1))) - 1) * (np.log(cdfvals) + np.log((1 - cdfvals[::(-1)])))).sum()) / nobs) - nobs)
    return asqu
