@article{AM2_1971__6_136204,
     author = {R.C. MULLIN and W.D. WALLIS},
     title = {On the {Existence} of {Room} {Squares} of {Order} 4n},
     journal = {Aequationes mathematicae},
     pages = {306--309},
     publisher = {mathdoc},
     volume = {6},
     year = {1971},
     zbl = {0236.05015},
     url = {http://geodesic.mathdoc.fr/item/AM2_1971__6_136204/}
}