Rules and structure of Arabic calligraphy
This is one of the reasons I love written Arabic. It is beautiful in a line or as an image.
an overview of calligraphic kufic variations of the word "Allah":
Calligraphy arabe by rachidbenour.deviantart.com on @deviantART
Ottoman Calligraphy with Illumination | İpek-İş | İpek-İş