Update the documentation.

README.md

@@ -18,12 +18,12 @@ recovery using GRACE type satellite observations.
 
 <!-- vim-markdown-toc GitLab -->
 
-* [Requirements](#requirements)
-* [Installation](#installation)
-* [Usage](#usage)
-* [Performance](#performance)
-* [Files](#files)
-* [Contributors](#contributors)
+- [Requirements](#requirements)
+- [Installation](#installation)
+- [Usage](#usage)
+- [Performance](#performance)
+- [Files](#files)
+- [Contributors](#contributors)
 
 <!-- vim-markdown-toc -->
 
@@ -40,7 +40,7 @@ Toolbox](https://de.mathworks.com/help/distcomp/).
 
 ## Installation
 
-Download gracetools as a zip file and extract it somewhere on your computer.
+Download GRACETOOLS as a zip file and extract it somewhere on your computer.
 
 - [**gracetools.zip**](https://gitlab.aei.uni-hannover.de/geoq/gracetools/-/archive/master/gracetools-master.zip)
 
@@ -148,14 +148,15 @@ days of observation, each iteration takes about 1h 10min.
 - `plmsp.m`- fully normalized associated Legendre functions for all degree and
   order but in a single points
 - `readACC.m`- Read GRACE ACC1B
-- `readGFC.m`- Read GFC file
+- `readGFC.m`- Read Gravity Field Coefficients (GFC file)
 - `readGNV.m`- Read GRACE GNV1B
 - `readKBR.m`- Read GRACE KBR1B
 - `readSCA.m`- Read GRACE SCA1B
-- `Ri2e.m`- returns the rotation matrix from an inertial frame to an
-  Earth-fixed coordinate system
-- `Ri2e_dot.m`- returns the derivative of the rotation matrix from inertial
-  frame to an Earth-fixed Earth-centered coordinate system
+- `Ri2e.m`- returns the rotation matrix (only Z-rotation) from an inertial
+  frame to an Earth-fixed coordinate system
+- `Ri2e_dot.m`- returns the derivative of the rotation matrix (only Z-rotation)
+  from inertial
+  frame to an Earth-fixed coordinate system
 - `save_vars2continue_itr.m`- save all important variables of a gravity
   estimation
 - `vec2cs.m`- rearranges a vector shaped set of spherical harmonic coefficients