Hassan Dahab Mohamed, N. O. Kheiry Abdalla, Ahmed Gafar Elfaki Montasir, Effect of Hours of Use and Age in Years in Estimating Repair and Maintenance Costs for Two Sizes of Agricultural Tractors in Northern Sudan, Journal of Agronomy Research, Volume 4, Issue 2, 2021, Pages 1-11, ISSN 2639-3166, https://doi.org/10.14302/issn.2639-3166.jar-21-3875. (https://openaccesspub.orgjar/article/1710) Keywords: Repair and Maintenance; purchase price; Hours of Use; Age; Tractor; New Halfa.