diff --git a/README.md b/README.md
index 4f959de..91e6732 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,5 @@
 # school-work-numerical-analysis
 
+https://tutorial.math.lamar.edu/classes/de/RepeatedRoots.aspx
+
+https://math.libretexts.org/Bookshelves/Analysis/Supplemental_Modules_(Analysis)/Ordinary_Differential_Equations/3%3A_Second_Order_Linear_Differential_Equations/3.1%3A_Homogeneous_Equations_with_Constant_Coefficients
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