diff --git a/3-perception/vhar-system/1-introduction.tex b/3-perception/vhar-system/1-introduction.tex
index 3d0fa92..9d06164 100644
--- a/3-perception/vhar-system/1-introduction.tex
+++ b/3-perception/vhar-system/1-introduction.tex
@@ -2,8 +2,9 @@
 \label{intro}
 
 One approach to render virtual haptic textures consists in simulating the roughness of a periodic grating surface as a vibrotactile sinusoidal (\secref[related_work]{texture_rendering}).
-The vibrations are rendered to a voice-coil actuator embedded in a hand-held tool or worn on the finger, but to create the illusion of touching a pattern with a fixed spatial period, the frequency of signal must be modulated according to the finger movement.
-Previous work either used mechanical system to track the movement at high frequency \cite{strohmeier2017generating,friesen2024perceived}, or required the user to move at a constant speed  to keep the signal frequency constant \cite{asano2015vibrotactile,ujitoko2019modulating}.
+The vibrations are rendered to a voice-coil actuator embedded in a hand-held tool or worn on the finger.
+To create the illusion of touching a pattern with a fixed spatial period, the frequency of signal must be modulated according to the finger movement.
+Previous work either used mechanical system to track the movement at high frequency \cite{strohmeier2017generating,friesen2024perceived}, or required the user to move at a constant speed to keep the signal frequency constant \cite{asano2015vibrotactile,ujitoko2019modulating}.
 However, this method has not yet been integrated in an \AR headset context, where the user should be able to freely touch and explore the visuo-haptic texture augmentations.
 
 %which either constrained hand to a constant speed to keep the signal frequency constant \cite{asano2015vibrotactile,friesen2024perceived}, or used mechanical sensors attached to the hand \cite{friesen2024perceived,strohmeier2017generating}