Ndayirukiye, A., F. Ndikuryayo, P. C. Mpawenayo, J. Ngezahayo, and G. Gahungu. “Theophylline and Caffeine Content in Black Tea Produced in Burundi”. European Scientific Journal, ESJ, Vol. 22, no. 6, Feb. 2026, p. 59, doi:10.19044/esj.2026.v22n6p59.