README.md

-4C open source publication
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+README 4C - FORSEE - FORESt Ecosystems in a changing Environment
+
+This file contains basic information on the open source distribution of
+the computer simulation forest model 4C. The model has been developed and is maintained
+at the Potsdam Institute for Climate Impact Research (PIK) in Potsdam, Germany,
+see "opensource_PIK_approval".
+
+All source code and documents provided are subject to copyright (c) by the 
+Potsdam Institute for Climate Impact Research. All files are licenced under 
+BSD 2-Clause License, see the LICENCE file for details. The 4C model is a 
+collaborative work, see the AUTHOR file for details.
+
+- See http://www.pik-potsdam.de/4c/ for information about 4C and the manual
+- For the model description see 4C_description.pdf in the directory descriptions
+- The directory executables contains three executables with self-explanatory names
+- The directory source_code contains the corresponding source codes in three subdirectories with self-explanatory names
+- Additional information can be found in following directories:
+    * manuals: about "how to start" and " generate exe"  
+    * descriptions/additional: background information documents 
+    * descriptions/Fact_sheets: short summary of the model in English and German
+    * source_code/additional: overview on variables with their names in the 4C description and the names in the source code
+                              flow chart of the model 4C 
+    * test_data_sets: test the correct function mode of the model with complete sets of input data and control files 
+    * publications: relevant publications regarding the model 4C
+
+The source code is distributed via a git repository at: 
+https://gitlab.pik-potsdam.de/foresee/4C and is ready to use.
+The code language is Fortran90. Since the model development is
+finished, there is no further development and no further support in model 
+download, setup, development or application. No merge or other development 
+requests will be handeled. Therefore there are no code style recommendations or
+instructions on how to create source code amendments.
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