Little's Law in a continuous setting

In this paper we show that the recently introduced ‘input-weighted average lead-time’ is equivalent to the average lead-time measured per item. Furthermore, we state that measuring the average lead-time does not depend on knowing the applied priority rule. Consequently, the relationship ‘average lead-time is equal to the fraction average inventory over average utilization’ holds true for every priority rule. Altogether this can be seen as Little's Law in a continuous setting.