Add users: OpenPTrack and IAS-Lab@Univ. of Padova

Change-Id: I841aeddb0f0c2b0d905fc0520553f263db7e7959

docs/source/users.rst

diff --git a/docs/source/users.rst b/docs/source/users.rst
index 20f0e18..ed54f8b 100644
--- a/docs/source/users.rst
+++ b/docs/source/users.rst
@@ -15,7 +15,7 @@
     Tango`_.
 
 * `Willow Garage`_ uses Ceres to solve `SLAM`_ problems.
-* `Southwest Research Insitute <http://www.swri.org/>`_ uses Ceres for
+* `Southwest Research Institute <http://www.swri.org/>`_ uses Ceres for
   `calibrating robot-camera systems`_.
 * `Blender <http://www.blender.org>`_ uses Ceres for `planar
   tracking`_ and `bundle adjustment`_.
@@ -36,6 +36,14 @@
   * Large scale optimization of visual, inertial, gps and
     wheel-odometry data for long term autonomy.
 
+* `OpenPTrack <http://openptrack.org/>`_ uses Ceres for camera
+  calibration.
+* The `Intelligent Autonomous System Lab <http://robotics.dei.unipd.it/>`_
+  at University of Padova, Italy, uses Ceres for
+
+  * Camera/depth sensors network calibration.
+  * Depth sensor distortion map estimation.
+
 .. _bundle adjustment: http://en.wikipedia.org/wiki/Structure_from_motion
 .. _Street View: http://youtu.be/z00ORu4bU-A
 .. _PhotoTours: http://google-latlong.blogspot.com/2012/04/visit-global-landmarks-with-photo-tours.html