  This article addresses the problem of existence of local factors, i.e., the
root numbers and L-functions attached to representations of reductive groups
over local fields and irreducible finite dimensional representations of their
L-groups, as well as their equality with those of Artin factors through the
local Langlands correspondence. We conclude the paper with a survey of the
theory of monoids of Braverman-Kazhdan, Ngo and Vinberg in generalizing the
method of Godement and Jacquet to arbitrary setting and their connections with
Langlands-Shahidi method.
