def hull_book_tests():
    """
    Example 17.1, page 355, Hull:

    >>> S = 49
    >>> K = 50 
    >>> r = .05
    >>> t = 0.3846
    >>> sigma = 0.2
    >>> flag = 'c'
    >>> delta_calc = delta(flag, S, K, t, r, sigma)
    >>> # 0.521601633972
    >>> delta_text_book = 0.522
    >>> abs(delta_calc - delta_text_book) < .01
    True

    Example 17.2, page 359, Hull:

    >>> S = 49
    >>> K = 50 
    >>> r = .05
    >>> t = 0.3846
    >>> sigma = 0.2
    >>> flag = 'c'
    >>> annual_theta_calc = theta(flag, S, K, t, r, sigma) * 365
    >>> # -4.30538996455
    >>> annual_theta_text_book = -4.31
    >>> abs(annual_theta_calc - annual_theta_text_book) < .01
    True

    Example 17.4, page 364, Hull:

    >>> S = 49
    >>> K = 50 
    >>> r = .05
    >>> t = 0.3846
    >>> sigma = 0.2
    >>> flag = 'c'
    >>> gamma_calc = gamma(flag, S, K, t, r, sigma)
    >>> # 0.0655453772525
    >>> gamma_text_book = 0.066
    >>> abs(gamma_calc - gamma_text_book) < .001
    True

    Example 17.6, page 367, Hull:
    
    >>> S = 49
    >>> K = 50 
    >>> r = .05
    >>> t = 0.3846
    >>> sigma = 0.2
    >>> flag = 'c'
    >>> vega_calc = vega(flag, S, K, t, r, sigma)
    >>> # 0.121052427542
    >>> vega_text_book = 0.121
    >>> abs(vega_calc - vega_text_book) < .01
    True

    Example 17.7, page 368, Hull:

    >>> S = 49
    >>> K = 50 
    >>> r = .05
    >>> t = 0.3846
    >>> sigma = 0.2
    >>> flag = 'c'
    >>> rho_calc = rho(flag, S, K, t, r, sigma)
    >>> # 0.089065740988
    >>> rho_text_book = 0.0891
    >>> abs(rho_calc - rho_text_book) < .0001
    True
    """
