Zhang , QixianLiu , Jicai and Guan , Qiang. (2021). The Additive-Multiplicative Hazards Model for Multiple Type of Recurrent Gap Times.
            <i>Communications in Mathematical Research </i>. <i>31</i> (2).
            97-107.
         doi:10.13447/j.1674-5647.2015.02.01