Update README.md with LGMRES(m) info

README.md

@@ -24,6 +24,15 @@ Variant of the restarted GMRES that employs a Proportional-Derivative (PD) contr
 [x, flag, relresvec, mvec, time] = pd_gmres(A, b, mInitial, mMinMax, mStep, tol, maxit, xInitial, alphaPD)
 ```
 
+### LGMRES(*m*) ([Baker & Jessup & Manteuffel, 2005](https://epubs.siam.org/doi/abs/10.1137/S0895479803422014))
+
+Modified implementation of the restarted GMRES performed that appends *k* error approximation vectors to the restarting Krylov
+subspace, as a way to preserve information from previously discarted search subspaces.
+
+```Matlab
+[x, flag, relresvec, time] = lgmres(A, b, m, k, tol, maxit, xInitial)
+```
+
 ## Contributing
 
 If you wish to contribute to KrySBAS, please read the [developer guide](https://github.com/nidtec-una/krysbas-dev/blob/dev_guide/dev_guide.md) before opening a pull request.