5Skinner W A, Crawford H T, Rutledge L C, et al. Topi- cal mosquito repellants Ⅻ: N-substituted ureas and cyclic ureas[J]. Journal of Pharmaceutical Sciences, 1979, 68(3): 391-392.
6Jochem H, Theodor W, Thorsten R, et al. Method for the continuous production of tetra-substituted ureas:US, 7053244[P].2006.