@article{10_4064_am_13_4_493_496,
     author = {R. Zieli\'nski},
     title = {A simplex design for gradient estimation in quadratic regression},
     journal = {Applicationes Mathematicae},
     pages = {493--496},
     publisher = {mathdoc},
     volume = {13},
     number = {4},
     year = {1972},
     doi = {10.4064/am-13-4-493-496},
     zbl = {0281.62077},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/am-13-4-493-496/}
}