G. W. Hoffmann, "Incorporation of a Non-specific T Cell Dependent Helper Factor into a Network Theory of the Regulation of the Immune Response", in "Theoretical Immunology", G.I. Bell, A.S. Perelson and G.H. Pimbley (eds.) Marcel Dekker, N.Y., (1978) pp. 571-602.

In the first symmetrical network paper only antigen-specific and anti-idiotypic T cell factors were included. In this paper a non-specific T cell factor was added, which expanded the scope of the theory significantly. The phenomena that could now be explained included responses to T independent antigens, hapten-carrier conjugates, and the need for two signals to induce B cells to make antibodies.