Update readme

README.md

@@ -7,14 +7,26 @@ Requirements
 ------------
 ------------
 
 
 The code for this library was written in C++17. You therefore need a
 The code for this library was written in C++17. You therefore need a
-recent compiler to build it. For the development gcc 9.3 and clang 9.0
+recent compiler to build it. For the development gcc 9.4 and clang 9.0
 have been used as well as MSVC version 2019.
 have been used as well as MSVC version 2019.
 
 
 Other requirements are:
 Other requirements are:
 
 
 - [mrc](https://github.com/mhekkel/mrc), a resource compiler that
 - [mrc](https://github.com/mhekkel/mrc), a resource compiler that
   allows including data files into the executable making them easier to
   allows including data files into the executable making them easier to
-  install. Strictly this is optional, but at the expense of functionality.
+  install. Strictly speaking this is optional, but at the expense of
+  functionality.
+- [libeigen](https://eigen.tuxfamily.org/index.php?title=Main_Page), a
+  library to do amongst others matrix calculations. This usually can be
+  installed using your package manager, in Debian/Ubuntu it is called
+  `libeigen3-dev`
+- zlib, the development version of this library. On Debian/Ubuntu this
+  is the package `zlib1g-dev`.
+- [boost](https://www.boost.org). The boost libraries are only needed if
+  you want to build the testing code.
+
+When building using MS Visual Studio, you will also need [libzeep](https://github.com/mhekkel/libzeep)
+since MSVC does not yet provide a C++ template required by libcifpp.
 
 
 Building
 Building
 --------
 --------
@@ -26,7 +38,7 @@ On linux e.g. you would issue the following commands to build and install
 libcifpp in your `$HOME/.local` folder:
 libcifpp in your `$HOME/.local` folder:
 
 
 ```bash
 ```bash
- git clone https://github.com/PDB-REDO/libcifpp.git
+ git clone https://github.com/PDB-REDO/libcifpp.git --recurse-submodules
  cd libcifpp
  cd libcifpp
  cmake -S . -B build -DCMAKE_INSTALL_PREFIX=$HOME/.local -DCMAKE_BUILD_TYPE=Release
  cmake -S . -B build -DCMAKE_INSTALL_PREFIX=$HOME/.local -DCMAKE_BUILD_TYPE=Release
  cmake --build build
  cmake --build build