Debian source control files -- ".dsc"
http://www.debian.org/doc/debian-policy/ - Debian Policy : Control files and their fields
Debian source .dsc file describes a source package. This file contains a series of fields, identified and separated just like the fields in the control file of a binary package.
This source package control file is generated by dpkg-source when it builds the source archive.
http://www.debian.org/doc/maint-guide/ - Maintainer guide.