[e2e] Literature on VoIP traffic models

Hi folks,

I'm looking for literature on VoIP traffic models. 
Could anyone suggest me some links? 

Specifically, I'm looking for electronic version of the following papers:

1. John N. Daigle and Joseph D. Langford. Models for analysis of packet
voice communications systems. IEEE JSAC, September, 1986.

2. Harry Jeffes and David. M. Lucantoni. A Markov modulated
charaterization of packetized voice and data traffic and related
statistical multiplexer performance, IEEE JSAC, September, 1986.

Any help is highly appreciated and many thanks in advance.

Tuan Anh Trinh

PhD student
High Speed Networks Lab
Technical University of Budapest