Update README.md

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src/GenericDetectors/pid/README.md

 Generic PID detectors
+=========================
 
-Electron-Ion Collider Detector Requirements and  R&D Handbook
-http://www.eicug.org/web/sites/default/files/EIC_HANDBOOK_v1.2.pdf
+List of references
+---------------------------
 
-Performance of the LHCb RICH detector at the LHC
-https://doi.org/10.1140/epjc/s10052-013-2431-9
+* [Electron-Ion Collider Detector Requirements and  R&D Handbook](http://www.eicug.org/web/sites/default/files/EIC_HANDBOOK_v1.2.pdf)
+* [Performance of the LHCb RICH detector at the LHC](https://doi.org/10.1140/epjc/s10052-013-2431-9)
+* [The PHENIX ring imaging Cherenkov detector](https://doi.org/10.1016/S0168-9002(00)00645-8)
+* [A ring imaging Cherenkov detector for CLAS12](https://doi.org/10.1016/j.nima.2013.08.012)
+* [Design and construction of a Cherenkov detector for Compton polarimetry at the ILC](https://iopscience.iop.org/article/10.1088/1748-0221/7/01/P01019)
+* [Bigbite Gas Cherenkov](http://wm-jlab.physics.wm.edu/mediawiki/index.php/Bigbite_Gas_Cherenkov)
+* Book: Gaseous Radiation Detectors: Fundamentals and Applications
 
-The PHENIX ring imaging Cherenkov detector
-https://doi.org/10.1016/S0168-9002(00)00645-8
 
-A ring imaging Cherenkov detector for CLAS12
-https://doi.org/10.1016/j.nima.2013.08.012
+List of detectors
+---------------------------
 
-Design and construction of a Cherenkov detector for
-Compton polarimetry at the ILC
-https://iopscience.iop.org/article/10.1088/1748-0221/7/01/P01019
+- Skeleton RICH detector: GenericRICH_geo.cpp
 
-Bigbite Gas Cherenkov
-http://wm-jlab.physics.wm.edu/mediawiki/index.php/Bigbite_Gas_Cherenkov
 
-Book: Gaseous Radiation Detectors: Fundamentals and Applications
 
-
-=====================
-
-- GenericRICH_geo.cpp
-Skeleton RICH detector