Yongjie Piao ,  and Jin , Hailan. (2012). Existence Problems of Additive Selection Maps for Another Type Subadditive Set-Valued Map.
            <i>Analysis in Theory and Applications</i>. <i>28</i> (3).
            294-300.
         doi:10.3969/j.issn.1672-4070.2012.03.010