diff --git a/phd-thesis.org b/phd-thesis.org
index 3056e7c..31ff19b 100644
--- a/phd-thesis.org
+++ b/phd-thesis.org
@@ -5376,7 +5376,7 @@ Some degrees of freedom, particularly the vertical translation and rotation abou
 A key advantage of this approach is that the control performance can be tuned individually for each direction.
 This is particularly valuable when performance requirements differ between directions - for instance, when higher positioning accuracy is required vertically than horizontally, or when certain rotational degrees of freedom can tolerate larger errors than others.
 
-However, significant coupling exists between certain degrees of freedom, particularly between rotations and translations (e.g., $\epsilon_{R_x}/\mathcal{F}_y$ or $\epsilon_{D_y}/\bm\mathcal{M}_x$).
+However, significant coupling exists between certain degrees of freedom, particularly between rotations and translations (e.g., $\epsilon_{R_x}/\mathcal{F}_y$ or $\epsilon_{D_y}/\mathcal{M}_x$).
 
 For the conceptual validation of the acrshort:nass, control in the strut space was selected due to its simpler implementation and the beneficial decoupling properties observed at low frequencies.
 More sophisticated control strategies will be explored during the detailed design phase.