求翻译：付款方式：买方应于2002年3月30日前通过德国国家银行开立以卖方为受益人的即期不可撤销信用证，有效期至装运后30天在中国议付。即期信用证。是什么意思？

Payment: Buyer shall on March 30, 2002 by the German National Bank spot irrevocable letter of credit opened in favor of the seller, valid until shipment after 30 days in China for negotiation. Sight.

Payment method: the buyer should be in March 2002 by 30 National Bank opened by Germany to the seller for the benefit of the irrevocable letter of credit, and is valid until 30 days after shipping and in China. The letters of credit.

Payment method: The buyer should draw up immediate take the seller before March 30, 2002 through Germany State bank cannot abolish the letter of credit as the beneficiary, the term of validity to ships latter 30 day in the Chinese negotiation.Immediate letter of credit.

Method of payment: the buyer should be passed prior to March 30, 2002 Germany State Bank opened in the immediate irrevocable letter of credit in favour of the seller, valid until 30 days after shipment in China for negotiation. Sight letter of credit.

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