Update pid README

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
+
+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
+
+
 =====================
 
 - GenericRICH_geo.cpp