Update README

Author: kmokstad

README.md

@@ -1,6 +1,11 @@
 # IFEM-ShellEx
 
 A shell FE application using external element routines.
+This application is based on unstructured Lagrange interpolation
+(the [ASMu2DLag](https://github.com/OPM/IFEM/blob/master/src/ASM/ASMu2DLag.h) class),
+and can read FE models from Nastran bulk data files.
 
-The ANDES shell element routines used here are from the
-[fedem-solvers](https://github.com/openfedem/fedem-solvers) project.
+The Fortran source code of ANDES shell element used here are from the
+[fedem-solvers](https://github.com/openfedem/fedem-solvers) project,
+whereas the code in the FFlLib sub-folder are from the related
+[fedem-foundation](https://github.com/openfedem/fedem-foundation) project.