Databases This category references specific databases, as well as database networks and commercial data service providers (which provide access to many databases). When feasible both the network and the individual components of the network are referenced as separate listings. Databases are commonly offered over the Internet, through electronic bulletin boards (BBSs), through fax-on-demand systems, on CD-ROMs and diskettes and in hardcopy format. Note: Some databases are free online or via download, while others are available for purchase or use on a fee basis. Related References A discussion of databases and online systems is provided in the EnviroSource Subject Guide titled Databases/Online Systems Guide. Databases that are specific to another EnviroSource category are referenced in the other category. For example, a database of treatment technologies would be found in the category Treatment Technologies. This provides more specificity when browsing, i.e. references here do not fit better into other categories. Listings referenced in the EnviroSource category Information Directories may be similar to those referenced in this category.