Analysis of MAP1I, PH2O/PH1I, PH2O/1 retrial queue with two-way communication, optional service, single vacation, closedown, setup and balking. - G. Ayyappan; G. Archana Alias Gurulakshmi; B. Somasundaram (Int. J. Math. Oper. Res., 2022)

Analysis of MAP/PH/1 queue with differentiated vacation, vacation interruption under N-policy, optional service, breakdown, repair, setup and discouragement of customers. - G. Ayyappan; G. Archana Alias Gurulakshmi (Int. J. Math. Oper. Res., 2024)

Analysis of MAP/PH/1 queueing system with discarding customers having imperfect service, single vacation, feedback and impatient customers. - G. Ayyappan; G. Archana Alias Gurulakshmi (Int. J. Math. Oper. Res., 2024)

A two-server tandem queueing model with Markovian arrival process, phase type service, working vacation, feedback, re-service, unreliable server, interrupted closedown and customers intolerance. - G. Ayyappan; G. Archana Alias Gurulakshmi (Int. J. Math. Oper. Res., 2025)