DOUBLE PRECISION FUNCTION LAMNF(NF,LAMBDA5) - Calculation of $\Lambda_{\overline{\rm MS}}^{(n_f)}$

This routine calculates $\Lambda_{\overline{\rm MS}}^{(n_f<5)}$ from $\Lambda_{\overline{\rm MS}}^{(5)}$ to order $\alpha_{\overline{\rm MS}}^3$, according to Eq. (9.7) from Ref. [1]. For $n_f<3$, $\Lambda_{\overline{\rm MS}}^{(3)}$ is used.