For each shipment, two or three negotiable or signed bills of lading are usually issues, plus as many non-negotiable copies as may be required.
通常都需要开出两到三份可转让或签名提单，外加根据需要提交的若干份提单副本。
2
As negotiable securities, bills can be current by transferring rights.
票据是流通证券，其流通是通过票据权利的转让实现的。
3
"Commercial bills" refer to negotiable and transferable debt instruments issued by the issuing body for a period of between 2 days and 270 days to meet the demands of liquid assets.