SGML says nothing about how a document should be displayed to the user, or rendered on paper. To do that, various languages have been developed to describe stylesheets, including DynaText, Panorama, SPICE, JSSS, FOSI, CSS, and DSSSL. For DocBook, we are using stylesheets written in DSSSL. For HTML we are using CSS. The Documentation Project uses a slightly customised version of Norm Walsh's modular DocBook stylesheets. These can be found in textproc/dsssl-docbook-modular.