This document may be used under the terms the GNU General Public License version 3 or higher. `Conditions for copying and translations can be found at http://xinocat.com/refcard/, where you can always get the latest version of the reference card.The license text can be found at http://www.gnu.org/copyleft/gpl.html and /usr/share/common-licenses/GPL-3. AbstractThe idea of this reference card is to