my multiple citations are shown like that : [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30].
instead of : [6-30]
even though I am using IEEE style
why? is it a bug ? what could I do?