Lutz, D., Sturm, E., Tacconi, L. J., Valiante, E., Schweitzer, M., Netzer, H., et al. (2007). PAH emission and star formation in the host of the z~2.56 cloverleaf QSO. Astrophysical Journal, 661(1 Part 2), L25-L28. doi:10.1086/518537.