Rituparna Chutia Florentin Smarandache Ranking of single-valued neutrosophic numbers through the index of optimism and its reasonable properties. 1489-1518 2022 55 Artif. Intell. Rev. 2 https://doi.org/10.1007/s10462-021-09981-3 db/journals/air/air55.html#ChutiaS22