6d026765_Plugin_YAML___BukkitWiki_Attributes_Notes
[Attribute] depend [Required] no [Description] A list of plugins that your plugin requires to load. [Example] depend: [OnePlugin, AnotherPlugin] [Notes] 
The value must be in YAML list format (See http://en.wikipedia.org/wiki/YAML#Lists ) Use the "name" attribute of the required plugin in order to specify the dependency. If any plugin listed here is not found your plugin will fail to load. If multiple plugins list each other as a depend, so that there are no plugins without an unloadable dependency, all will fail to load. (See: Wiki: Plugin_Dependencies)
Plugin YAML - BukkitWiki
Notes