Snehasish Bose, P. Muthukumar and Jaydeb Sarkar, Beurling type invariant subspaces of composition operators, J. Operator Theory, 86 (2), 2021, 425--438.
P. Muthukumar and S. Ponnusamy, Composition operators on Hardy spaces of the homogenous rooted trees, Monatsh. Math. 192 (3), 2020, 721--743.
P. Muthukumar and S. Ponnusamy, Weighted composition operators on the class of subordinate functions, Rocky Mountain J. Math. 48 (6), 2018, 2055--2068.
P. Muthukumar, S. Ponnusamy and Herve Queffelec, Estimate for norm of a composition operator on the Hardy-Dirichlet space, Integral Equations and Operator Theory 90 (1), 2018, Art. 11, 12pp.
P. Muthukumar and S. Ponnusamy, Composition operators on the discrete Hardy space on homogenous trees, Bull. Malays. Math. Sci. Soc. 40 (4), 2017, 1801--1815.
P. Muthukumar and S. Ponnusamy, Discrete analogue of generalized Hardy spaces and multiplication operators on homogenous trees, Anal. Math. Phys. 7 (3), 2017, 267--283.