Kulinski T, Olejniczak M, Huthoff H, Bielecki L, Pachulska-Wieczorek K, Das AT, Berkhout B, Adamiak RW. The Apical Loop of the HIV-1 TAR RNA Hairpin Is Stabilized by a Cross-loop Base Pair. Journal of Biological Chemistry. 2003 Oct;278(40):38892–901. doi: 10.1074/jbc.m301939200.