diff --git a/README.md b/README.md
index 040f1134f..88f69dec4 100644
--- a/README.md
+++ b/README.md
@@ -1,59 +1,77 @@
-README - Georgia Tech Smoothing and Mapping library
-===================================================
-
-What is GTSAM?
---------------
-
-GTSAM is a library of C++ classes that implement smoothing and
-mapping (SAM) in robotics and vision, using factor graphs and Bayes
-networks as the underlying computing paradigm rather than sparse
-matrices.
-
-On top of the C++ library, GTSAM includes a MATLAB interface (enable
-GTSAM_INSTALL_MATLAB_TOOLBOX in CMake to build it). A Python interface
-is under development.
-
-Quickstart
-----------
-
-In the root library folder execute:
-
-```
-#!bash
-$ mkdir build
-$ cd build
-$ cmake ..
-$ make check (optional, runs unit tests)
-$ make install
-```
-
-Prerequisites:
-
-- [Boost](http://www.boost.org/users/download/) >= 1.43 (Ubuntu: `sudo apt-get install libboost-all-dev`)
-- [CMake](http://www.cmake.org/cmake/resources/software.html) >= 2.6 (Ubuntu: `sudo apt-get install cmake`)
-- A modern compiler, i.e., at least gcc 4.7.3 on Linux.
-
-Optional prerequisites - used automatically if findable by CMake:
-
-- [Intel Threaded Building Blocks (TBB)](http://www.threadingbuildingblocks.org/) (Ubuntu: `sudo apt-get install libtbb-dev`)
-- [Intel Math Kernel Library (MKL)](http://software.intel.com/en-us/intel-mkl)
-
-GTSAM 4 Compatibility
----------------------
-
-GTSAM 4 will introduce several new features, most notably Expressions and a python toolbox. We will also deprecate some legacy functionality and wrongly named methods, but by default the flag GTSAM_ALLOW_DEPRECATED_SINCE_V4 is enabled, allowing anyone to just pull V4 and compile. To build the python toolbox, however, you will have to explicitly disable that flag.
-
-Also, GTSAM 4 introduces traits, a C++ technique that allows optimizing with non-GTSAM types. That opens the door to retiring geometric types such as Point2 and Point3 to pure Eigen types, which we will also do. A significant change which will not trigger a compile error is that zero-initializing of Point2 and Point3 will be deprecated, so please be aware that this might render functions using their default constructor incorrect.
-
-Additional Information
-----------------------
-
-Read about important [`GTSAM-Concepts`](GTSAM-Concepts.md) here.
-
-See the [`INSTALL`](INSTALL) file for more detailed installation instructions.
-
-GTSAM is open source under the BSD license, see the [`LICENSE`](LICENSE) and [`LICENSE.BSD`](LICENSE.BSD) files.
-
-Please see the [`examples/`](examples) directory and the [`USAGE`](USAGE.md) file for examples on how to use GTSAM.
-
+README - Georgia Tech Smoothing and Mapping library
+===================================================
+
+What is GTSAM?
+--------------
+
+GTSAM is a library of C++ classes that implement smoothing and
+mapping (SAM) in robotics and vision, using factor graphs and Bayes
+networks as the underlying computing paradigm rather than sparse
+matrices.
+
+On top of the C++ library, GTSAM includes a MATLAB interface (enable
+GTSAM_INSTALL_MATLAB_TOOLBOX in CMake to build it). A Python interface
+is under development.
+
+Quickstart
+----------
+
+In the root library folder execute:
+
+```
+#!bash
+$ mkdir build
+$ cd build
+$ cmake ..
+$ make check (optional, runs unit tests)
+$ make install
+```
+
+Prerequisites:
+
+- [Boost](http://www.boost.org/users/download/) >= 1.43 (Ubuntu: `sudo apt-get install libboost-all-dev`)
+- [CMake](http://www.cmake.org/cmake/resources/software.html) >= 2.6 (Ubuntu: `sudo apt-get install cmake`)
+- A modern compiler, i.e., at least gcc 4.7.3 on Linux.
+
+Optional prerequisites - used automatically if findable by CMake:
+
+- [Intel Threaded Building Blocks (TBB)](http://www.threadingbuildingblocks.org/) (Ubuntu: `sudo apt-get install libtbb-dev`)
+- [Intel Math Kernel Library (MKL)](http://software.intel.com/en-us/intel-mkl)
+
+GTSAM 4 Compatibility
+---------------------
+
+GTSAM 4 will introduce several new features, most notably Expressions and a python toolbox. We will also deprecate some legacy functionality and wrongly named methods, but by default the flag GTSAM_ALLOW_DEPRECATED_SINCE_V4 is enabled, allowing anyone to just pull V4 and compile. To build the python toolbox, however, you will have to explicitly disable that flag.
+
+Also, GTSAM 4 introduces traits, a C++ technique that allows optimizing with non-GTSAM types. That opens the door to retiring geometric types such as Point2 and Point3 to pure Eigen types, which we will also do. A significant change which will not trigger a compile error is that zero-initializing of Point2 and Point3 will be deprecated, so please be aware that this might render functions using their default constructor incorrect.
+
+The Preintegrated IMU Factor
+----------------------------
+
+GTSAM includes a state of the art IMU handling scheme based on
+
+- Todd Lupton and Salah Sukkarieh, "Visual-Inertial-Aided Navigation for High-Dynamic Motion in Built Environments Without Initial Conditions", TRO, 28(1):61-76, 2012.
+
+Our implementation improves on this using integration on the manifold, as detailed in
+
+- Luca Carlone, Zsolt Kira, Chris Beall, Vadim Indelman, and Frank Dellaert, "Eliminating conditionally independent sets in factor graphs: a unifying perspective based on smart factors", Int. Conf. on Robotics and Automation (ICRA), 2014. 
+- Christian Forster, Luca Carlone, Frank Dellaert, and Davide Scaramuzza, "IMU Preintegration on Manifold for Efficient Visual-Inertial Maximum-a-Posteriori Estimation", Robotics: Science and Systems (RSS), 2015.
+
+If you are using the factor in academic work, please cite the publications above.
+
+In GTSAM 4 a new and more efficient implementation, based on integrating on the NavState tangent space and detailed in docs/ImuFactor.pdf, is enabled by default. To switch to the RSS 2015 version, set the flag **GTSAM_TANGENT_PREINTEGRATION** to OFF.
+
+
+
+Additional Information
+----------------------
+
+Read about important [`GTSAM-Concepts`](GTSAM-Concepts.md) here.
+
+See the [`INSTALL`](INSTALL) file for more detailed installation instructions.
+
+GTSAM is open source under the BSD license, see the [`LICENSE`](LICENSE) and [`LICENSE.BSD`](LICENSE.BSD) files.
+
+Please see the [`examples/`](examples) directory and the [`USAGE`](USAGE.md) file for examples on how to use GTSAM.
+
 GTSAM was developed in the lab of [Frank Dellaert](http://www.cc.gatech.edu/~dellaert) at the [Georgia Institute of Technology](http://www.gatech.edu), with the help of many contributors over the years, see [THANKS](THANKS).
\ No newline at end of file