2022. DB - Optimal Criterion Design to Estimate the Parameters of Some Proportional Hazards Model with Minimal Variance with Practical Application. Journal of Al-Rafidain University College For Sciences ( Print ISSN: 1681-6870 ,Online ISSN: 2790-2293 ). 50, 3 (Jan. 2022), 87–94. DOI:https://doi.org/10.55562/jrucs.v50i3.503.