RFCs:

[RFC 1701] Generic Routing Encapsulation (GRE).

[RFC 1702] Generic Routing Encapsulation over IPv4 networks.

[RFC 2117] Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification.

[RFC 2337] Intra-LIS IP multicast among routers over ATM using Sparse Mode PIM.

[RFC 2362] Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification.

[RFC 2784] Generic Routing Encapsulation (GRE).

[RFC 2932] IPv4 Multicast Routing MIB.

[RFC 2933] Internet Group Management Protocol MIB.

[RFC 2934] Protocol Independent Multicast MIB for IPv4.

[RFC 3032] MPLS Label Stack Encoding.

[RFC 3208] PGM Reliable Transport Protocol Specification.

[RFC 3446] Anycast Rendevous Point (RP) mechanism using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP).

Publications:

Davie, Bruce; Farinacci, Dino; Katz, Dave; Rekhter, Yakov; Rosen, Eric C.; Swallow, George.
Tag Switching Architecture Overview.
December 1997. Proceedings of the IEEE, Vol. 85, No. 12.