USANCE L/C AT 30 DAYS AFTER B/L DATE 给你一个文章，总结了信用证的很多英语说法，你看看吧
30days L/C after date of B/L
USANCE LETTER OF CREDIT OF 30 DAYS AFWTER B/L.
(USANCE) L/C AT 30 DAYS AFTER B/L DATE
