diff --git a/numerical_methods/durand_kerner_roots.c b/numerical_methods/durand_kerner_roots.c
index a0bf1ea9..b997ccb1 100644
--- a/numerical_methods/durand_kerner_roots.c
+++ b/numerical_methods/durand_kerner_roots.c
@@ -7,6 +7,11 @@
 #include <complex.h>
 #include "function_timer.h"
 
+/**
+ * Test the algorithm online:
+ * https://gist.github.com/kvedala/27f1b0b6502af935f6917673ec43bcd7
+ **/
+
 /***
  * Try the highly unstable Wilkinson's polynomial:
  * ./numerical_methods/durand_kerner_roots.c 1 -210 20615 -1256850 53327946 -1672280820 40171771630 -756111184500 11310276995381 -135585182899530 1307535010540395 -10142299865511450 63030812099294896 -311333643161390640 1206647803780373360 -3599979517947607200 8037811822645051776 -12870931245150988800 13803759753640704000 -8752948036761600000 2432902008176640000