Xiaohua Kong Radu Negulescu Larry Weidong Ying Refinement-based formal verification with heterogeneous timing. 359-370 2003 4 Int. J. Softw. Tools Technol. Transf. 3 https://doi.org/10.1007/s10009-002-0096-z db/journals/sttt/sttt4.html#KongNY03