10.It was not clear how many of the notes had been used to snort cocaine and how many had picked up traces from other bills.

• 目前并不清楚在该项研究中，有多少张钞票曾被用来当成吸食古柯碱的工具，又有多少钞票上的微量古柯碱是因为沾到其他钞票所致。