Reference intervals of serum copper, selenium, rubidium, zinc, and magnesium with evaluation of the influence of age, sex, and physical activity (D. Davcheva, G. . Kirova, D. . Terzieva, & K. Simitchiev , Trans.). (2026). Bulgarian Medical Journal, 20(2), 67-72. https://journals.mu-sofia.bg/index.php/bmj/article/view/1112