@article{JRAM_1994__449_153609,
     author = {B. Brent Gordon},
     title = {Algebraic cycles in families of abelian varieties over {Hilbert-Blumenthal} surfaces.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {149--172},
     publisher = {mathdoc},
     volume = {449},
     year = {1994},
     zbl = {0805.14024},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1994__449_153609/}
}