diff --git a/README.md b/README.md
index 8765675..7128ae4 100644
--- a/README.md
+++ b/README.md
@@ -74,16 +74,16 @@ Perturbed.py:
 	Driven undampded oscillators with a plane-wave perturbation.  Options are: pendulum and double-well potential.  These are driven nonlinear Hamiltonian systems.  When driven at small perturbation amplitude near the separatrix, chaos emerges.  These systems do not conserve energy, because there is a constant input and output of energy as the system reacts against the drive force.  Plots a two-dimensional Poincaré section.
 
 raysimple.py: 
-	Eikonal equation simulator.
+	Eikonal equation simulator.  (See: https://galileo-unbound.blog/2019/05/30/the-iconic-eikonal-and-the-optical-path/)
 
 SIR.py: 
-	SIR homogeneous COVID-19 model
+	SIR homogeneous COVID-19 model (See: https://galileo-unbound.blog/2020/03/22/physics-in-the-age-of-contagion-the-bifurcation-of-covid-19/)
 
 SIRS.py: 
-	SIRS homogeneous COVID-19 model
+	SIRS homogeneous COVID-19 model (See: https://galileo-unbound.blog/2020/07/20/physics-in-the-age-of-contagion-part-4-fifty-shades-of-immunity-to-covid-19/)
 
 SIRWave.py: 
-	Covid-19 second wave model
+	Covid-19 second wave model (See:https://galileo-unbound.blog/2020/04/06/physics-in-the-age-of-contagion-part-2-the-second-wave-of-covid-19/)
 
 StandMap.py: 
 	The Chirikov map, also known as the standard map, is a discrete itereated map with winding numbers and islands of stability.