@article{SM_1996_187_11_a1,
     author = {V. A. Gritsenko and V. V. Nikulin},
     title = {Igusa modular forms and 'the~simplest' {Lorentzian} {Kac--Moody} algebras},
     journal = {Sbornik. Mathematics},
     pages = {1601--1641},
     publisher = {mathdoc},
     volume = {187},
     number = {11},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1996_187_11_a1/}
}