l_6$ can be obtained from the lattice calculations of the electromagnetic pion radius and $\bar l_4$ from the scalar radius. These calculations have not yet reached a precision comparable to (\[eq:l6\]) and (\[eq:l4\]). The combination $\bar l_1-\bar l_2$ can be obtained from higher-order effects in the pion form factors. Again this value is not yet competitive with the one of (\[eq:l1l2\]).

In the continuum we cannot vary the pion mass but lattice QCD calculations can easily do this by varying the quark masses. The constants that influence this behaviour are thus much easier to obtain from lattice calculations. The quantities that are measured here are the variation of $F_\pi$ with the pion mass which gives $\bar l_4$ and the deviation of $M_\pi^2/(2B\hat m)$ from unity as a function of $M_\pi$ which gives $\bar l_3$. The lattice calculations are done in a number of physically different ways: with only up and down quarks, $N_f=2$, including the strange quark, $N_f=2+1$, and including the charm quark as well, $N_f=2+1+1$. In addition one often uses partially quenched conditions where valence and sea quarks have different masses. The last case, $N_f=2+1+1$, is pursued mainly by the ETM collaboration [@Baron:2011sf]. The case with $N_f=2+1$ has many 