The style, format, and information required in court documents differs from one jurisdiction to another, between different levels of courts in a system, and between different areas of law. Therefore, the companies that publish casebook and other legal materials often publish form books as well, offering selections specific to the location and type of practice in which their customers are engaged. Many publishers offer the forms in their books on computer discs. Some books may be accompanied by CD-ROMs or DVD-ROMs.