See page 161 of Muller et al. paper for the definition of molecular topological index.

REFERENCES

W. R. Muller, K. Szymanski, J. V. Knop and N. Trinajstich, "Molecular topological index", J. Chem. Inf. Comput. Sci., vol. 30 (1990), 160-163. See Table 2 on page 162 column 3.