[1] A. Berman and R. J. Plemmons: 
Nonnegative Matrices in the Mathematical Sciences. Academic, 1979; SIAM, 1994. 
MR 1298430[4] C. Dellacherie, S. Martínez and J. S. Martín: 
Description of the sub-Markov kernel associated to generalized ultrametric matrices: an algorithmic approach. Linear Algebra Appl. 318 (2000), 1–21. 
MR 1787220[5] M. Fiedler: 
Some characterizations of symmmetric inverse $M$-matrices. Linear Algebra Appl. 275–276 (1998), 179–187. 
MR 1628388[9] J. J. McDonald, R. Nabben, M. Neumann, H. Schneider and M. J. Tsatsomeros: 
Inverse tridiagonal $Z$-matrices. Linear and Multilinear Algebra 45 (1998), 75–97. 
MR 1665619[10] J. J. McDonald, M. Neumann, H. Schneider and M. J. Tsatsomeros: 
Inverse $M$-matrix inequalities and generalized ultrametric matrices. Linear Algebra Appl. 220 (1995), 329–349. 
MR 1334583[11] R. Nabben: 
A class of inverse $M$-matrices. Electron. J. Linear Algebra 7 (2000), 53–58. 
MR 1766201 | 
Zbl 0956.15012[12] R. Nabben and R. S. Varga: 
A linear algebra proof that the inverses of strictly ultrametric matrix is a strictly diagonally dominant are of Stieljes types. SIAM J. Matrix Anal. Appl. 15 (1994), 107–113. 
DOI 10.1137/S0895479892228237 | 
MR 1257620[13] R. Nabben and R. S. Varga: 
Generalized ultrametric matrices—a class of inverse $M$-matrices. Linear Algebra Appl. 220 (1995), 365–390. 
MR 1334586[14] M. Neumann: 
A conjecture concerning the Hadamard product of inverse of $M$-matrices. Linear Algebra Appl. 285 (1995), 277–290. 
MR 1653539