Update README with reference to color copy of paper

Added a reference to a color copy of the RAMDECOM paper in the README.

Author: andr1976

README.md

@@ -11,7 +11,8 @@ Calculation routine to calculate the decompression wave speed for pipeline desig
 This code is developed by Anders Andreasen and is open source and published under an [MIT license](https://gitlab.rambollgrp.com/anra/ramdecom/-/blob/main/LICENSE) . For pure fluids, calculations can be made using open source tools only ([CoolProp](www.coolprop.org)). However, if calculations shall be made for mixtures a [REFPROP](https://www.nist.gov/srd/refprop) license and installation is required.  
 
 ## Background and reference
-The methods implemented in RAMDECOM are described in more detail in an *open access* publication in [Simulation Notes Europe](https://www.sne-journal.org/fileadmin/user_upload_sne/SNE_Issues_OA/SNE_32_4/articles/sne.32.4.10622.tn.OA.pdf). If you use RAMDECOM, please cite this article 
+The methods implemented in RAMDECOM are described in more detail in an *open access* publication in [Simulation Notes Europe](https://www.sne-journal.org/fileadmin/user_upload_sne/SNE_Issues_OA/SNE_32_4/articles/sne.32.4.10622.tn.OA.pdf). If you use RAMDECOM, please cite this article. 
+A [color copy](paper/ramdecom_paper.pdf) is also included in this repository.
 
 ```
 @article{ramdecom,