diff --git a/source/calculus/notations.rst b/source/calculus/notations.rst
index adc7730..6a8ac2e 100644
--- a/source/calculus/notations.rst
+++ b/source/calculus/notations.rst
@@ -4,7 +4,13 @@ Differentiation Notations
 
 Leibniz's Notation
 -------------------
-https://www.me.psu.edu/cimbala/me420/Homework/dydx_quotient_article.html
+
+The derivative of a function :math:`f` at :math:`x` is given
+by :math:`\lim\limits_{h\to0} \frac{f(x+h)-f(x)}{h}`.
+
+The Leibniz's notation expresses the derivative of :math:`f` as :math:`\frac{dy}{dx}` with :math:`y=f(x)`.
+
+More details `here <https://www.me.psu.edu/cimbala/me420/Homework/dydx_quotient_article.html>`__.
 
 Lagrange's Notation
 -------------------