\langle r^2\rangle^\pi_V &=& 0.437\pm0.016~\mathrm{fm}^2,
\qquad
c^\pi_V = 3.85\pm0.60~\mathrm{GeV}^{-4}~.\end{aligned}$$ A more recent analysis using dispersive methods [@Ananthanarayan:2013dpa] reached $\langle r^2\rangle^\pi_V\in (0.42,0.44)~\mathrm{fm}^2$ and $c^\pi_V \in (3.79,4.00)~\mathrm{GeV}^{-4}$ in good agreement with the above but somewhat smaller errors.

Values of the LECs {#nf2fits}
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When looking at values of the LECs in two-flavour theory, the usual convention is to use the $\bar l_i$ defined in (\[eq:deflib\]). These are independent of the subtraction scale but do depend instead explicitly on the pion mass. For a subtraction scale $\mu=0.77$ GeV one should keep in mind that $$-\ln\frac{M_\pi^2}{\mu^2} = 3.42\,.$$ Values of the $\bar l_i$ around this value are thus dominated by the pion chiral logarithm.

The values of $\bar l_1$ and $\bar l_2$ were originally determined from the $D$-wave $\pi\pi$ scattering lengths in [@Gasser:1983yg]. The analysis in [@Colangelo:2001df] relies instead on the whole $\pi\pi$ scattering analysis and yields $$\label{eq:l1l2}
\bar l_1 = -0.4\pm0.6\,,\qquad \bar l_2 = 4.3\pm0.1\,.$$ The main sources of uncertainty are the input estimates of the $c_i^r$ for both.

$\bar l_3$ is very difficult to get from phenomenology. For this one needs to know how the pion mass depends on higher powers of $\hat m$. Putting an upper limit on this leads to the 