Homework submitted after that will not be graded but will be kept for reference.

迟于第二天交的作业将不被批改，但是留作参考。

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We urge you to read all of the instructions thoroughly before attempting the installation or operation of this water heater. This manual should be kept for future reference.

我们要求用户在安装或使用本热水器之前，阅读本说明书的所有内容。请妥善保管本手册，以备将来参考。

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Also, every letter communication has a record and can be kept for further reference when needed.

再者，每一份信件往来日后一旦需要，都有案可查。

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