Sekhawat, K., Shivay, Y. S., & Kumar, D. (2008). Porductivity and nutrient uptake of spring sunflower (Helianthus annuus) as influenced by nitrogen sources, sulphur and boron levels*. The Indian Journal of Agricultural Sciences, 78(1). https://epubs.icar.org.in/index.php/IJAgS/article/view/9776