@article{MET_1967__11_175333,
     author = {M.P. Singh},
     title = {On the {Efficiency} of {Systematic} {Sampling} in {Ratio} and {Product} {Estimation}},
     journal = {Metrika},
     pages = {199--205},
     publisher = {mathdoc},
     volume = {11},
     year = {1967},
     url = {http://geodesic.mathdoc.fr/item/MET_1967__11_175333/}
}