  The bootstrap program for 1+1-dimensional integrable Quantum Field Theories
(QFT's) is developed to a large extent for the Homogeneous sine-Gordon (HSG)
models. This program can be divided into various steps, which include the
computation of the exact S-matrix, Form Factors of local operators and
correlation functions, as well as the identification of the operator content of
the QFT and the development of various consistency checks. Taking as an input
the S-matrix proposal for the HSG-models, we confirm its consistency by
carrying out both a Thermodynamic Bethe Ansatz (TBA) and a Form Factor
analysis. In contrast to many other 1+1-dimensional integrable models studied
in the literature, the HSG-models break parity, both at the level of the
Lagrangian and S-matrix, and their spectrum includes unstable particles. These
features have specific consequences in our analysis which are given a physical
interpretation. By exploiting the Form Factor approach, we develop further the
QFT advocated to the HSG-models. We evaluate correlation functions of various
local operators of the model as well as Zamolodchikov's c-function and
$\Delta$-sum rules. For the $SU(3)_2$-HSG model we show how the form factors of
different local operators are interrelated by means of the momentum space
cluster property. We find closed formulae for all $n$-particle form factors of
a large class of operators of the $SU(N)_2$-HSG models. These formulae are
expressed in terms of universal building blocks which allow both a determinant
and an integral representation.
