Media type: E-Article Title: Managing Discretionary Services: A Review and Research Opportunities Contributor: Wang, Xiaofang; Huang, Rongyi; Gao, Junguang; Debo, Laurens G. imprint: Springer Science and Business Media LLC, 2021 Published in: Journal of Systems Science and Systems Engineering Language: English DOI: 10.1007/s11518-020-5476-y ISSN: 1004-3756; 1861-9576 Keywords: Information Systems ; Control and Systems Engineering Origination: Footnote: