Update README.md

README.md

@@ -95,7 +95,7 @@ Major changes and extensions to tailor this code to a specific problem are discu
   meshio-convert -h
   ```
 - **FEniCS:** In the current code only `/mesh/mesh.xml` is imported and since the geometry of mesh is a rectangle, boundaries are defined as straight lines. A good starting point on how to import boundaries as (.xml) file is explained in [FEniCS Q&A](https://fenicsproject.org/qa/2986/how-to-define-boundary-condition-for-mesh-generated-by-gmsh/) and [FEniCS Q&A](https://fenicsproject.org/qa/5337/importing-marked-mesh-for-parallel-use/) as well marking with Gmsh in [meshio GitHub](https://github.com/nschloe/meshio/issues/265) and migration from (.xml) to (.xdmf) in [FEniCS Q&A](https://fenicsproject.discourse.group/t/transitioning-from-mesh-xml-to-mesh-xdmf-from-dolfin-convert-to-meshio/412/49).
-- **PETSc:** It is integrated by FEniCS or more precisely Dolfin. In class index page of [Dolfin](https://fenicsproject.org/olddocs/dolfin/2019.1.0/cpp/classes.html), the access to native pointers of PETSc via class members is explained. Good examples are `/src/FEMTools.cpp` and `main.cpp` of this directory; the finite element method is implemented in native PETSc environment while the input arguments are originally Dolfin objects. Other interesting aspect is the maneuver on mesh regions `Dolfin::Function` nodes and respective `Dolfin::PETScVector` objects, which can be found in `main.cpp` and `/src/GeneralTools.cpp`. Form headers such as `/src/Poisson.h` should be regenerated from `/ufl/Poisson.ufl` on every system by command:
+- **PETSc:** It is integrated by FEniCS or more precisely Dolfin. In class index page of [Dolfin](https://fenicsproject.org/olddocs/dolfin/2019.1.0/cpp/classes.html), the access to native pointers of PETSc via class members is explained. Good examples are `/src/FEMTools.cpp` and `main.cpp` of this directory; the finite element method is implemented in native PETSc environment while the input arguments are originally Dolfin objects. Other interesting aspect is the maneuver on mesh regions `Dolfin::Function` nodes and respective `Dolfin::PETScVector` objects, which can be found in `main.cpp` and `/src/GeneralTools.cpp`. Form headers such as `/src/Poisson.h` should be regenerated from `/ufl/Poisson.ufl` and replaced for every system. The command for generating `.h` heasers is:
   ```shell
   ffc -l dolfin Poisson.ufl
   ```