Location of particular apt rpms

Is there a way to find out the provenance of particular apt rpms listed in Synaptic, ie which repository they are located in, the web address to reach them outside apt, and so on? -- Pob hwyl / Best wishes Kevin Donnelly www.kyfieithu.co.uk - Meddalwedd Rhydd yn Gymraeg www.cymrux.org.uk - Linux Cymraeg ar un CD!