Update README.md

Faares · web-flow · commit 2cefe8e64981 · 2024-01-29T18:15:49.000+03:00
diff --git a/README.md b/README.md
@@ -140,6 +140,9 @@ As the title says! recently, I become deep into special areas, and references be
 #### Harmonic Analysis
 > TODO
 
+#### Spectral Theory
+> TODO
+
 #### Measure Theory
 - *Tao, T.* An Introduction to Measure Theory. [[Online](https://terrytao.wordpress.com/books/an-introduction-to-measure-theory/)]
 
