Résume | In a paper published in 1959, Shimura presented an elegant calculation of the critical values of $L$-functions attached to elliptic modular forms using the first cohomology group. I will show that a similar calculation is possible for Hilbert modular forms over real quadratic fields using the second cohomology group. Explicit numerical examples calculated by this method will be presented. I will also show that we can deduce some information on periods which are not related to critical values by this method. |