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1 files changed, 3 insertions, 2 deletions

diff --git a/content/know/concept/maxwell-bloch-equations/index.pdc b/content/know/concept/maxwell-bloch-equations/index.pdc
index 3f090a2..e3a3680 100644
--- a/content/know/concept/maxwell-bloch-equations/index.pdc
+++ b/content/know/concept/maxwell-bloch-equations/index.pdc
@@ -5,6 +5,7 @@ publishDate: 2021-10-02
 categories:
 - Physics
 - Quantum mechanics
+- Two-level system
 - Electromagnetism
 
 date: 2021-09-09T21:17:52+02:00
@@ -78,8 +79,8 @@ $$\begin{aligned}
 \end{aligned}$$
 
 With these, the equations for $c_g$ and $c_e$ can be rewritten as shown below.
-Note that $\vb{E}^{-}$ and $\vb{E}^{+}$ include the driving plane wave,
-and the *rotating wave approximation* is still made:
+Note that $\vb{E}^{-}$ and $\vb{E}^{+}$ include the driving plane wave, and the
+[rotating wave approximation](/know/concept/rotating-wave-approximation/) is still made:
 
 $$\begin{aligned}
     \dv{c_g}{t}