Liu, Y.(1992). Cells that present both specific ligand and costimulatory activity are the most efficient inducers of clonal expansion of normal CD4 T cells. Proceedings of the National Academy of Sciences, 89(9), 3845-3849. doi:10.1073/pnas.89.9.3845

Liu, Y. "Cells That Present Both Specific Ligand and Costimulatory Activity Are the Most Efficient Inducers of Clonal Expansion of Normal CD4 T Cells". Proceedings of the National Academy of Sciences, 89.9 ( 1992 ): 3845-3849.