@article{Mohamed20211 title = "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 = "Journal of Agronomy Research", volume = "4", number = "2", pages = "1 - 11", year = "2021", note = "", issn = "2639-3166", doi = "https://doi.org/10.14302/issn.2639-3166.jar-21-3875", url = "http://oap-journals.infojar/article/1710", author = "Hassan Dahab Mohamed and N. O. Kheiry Abdalla and Ahmed Gafar Elfaki Montasir", keywords = "Repair and Maintenance", keywords = "purchase price", keywords = "Hours of Use", keywords = "Age", keywords = "Tractor", keywords = "New Halfa." }