@article{MET_1966__10_175296,
     author = {S.K. Gupta and J.K. Goyal},
     title = {Queues with {Batch} {Poisson} {Arrivals} and {Hyper-Exponential} {Service} {Time} {Distribution}},
     journal = {Metrika},
     pages = {171--178},
     year = {1966},
     volume = {10},
     zbl = {0154.19105},
     url = {http://geodesic.mathdoc.fr/item/MET_1966__10_175296/}
}