Known for introducing convolutional codes and establishing the binary erasure channel, Elias also contributed fundamental new concepts and techniques to source coding. His widely cited 1975 paper introduced universal representations of the integers, showing that the integers could be coded with binary codewords having the crucial property that no codeword is the prefix of another but with virtually no expansion of their length from that in standard binary coding.
Elias was not the first to work on universal source coding, but his approach was so simple and insightful that it influenced much, if not all, of subsequent research in universal source coding. One such further development came in Peter's own 1988 paper that gave practical and ingenious methods for compressing any stationary source down to its entropy (essentially by coding how long it had been since the current source symbol was last observed rather than by coding the symbol itself) and that provided many ideas which have been incorporated into later universal coding schemes.
