Sign In Error: The Security Server is down or cannot be reached.

登录错误：安全服务器关闭或无法达成。

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There are several things to notice above: first, there is no space on either side of the "=" sign; any space will result in an error (try it and see).

以上有几点注意事项：第一，在等号 "=" 的两边没有空格，任何空格将导致错误（试一下看看）。

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The methods of sign test and runs number test of negligence error and adjustment of experimental covariance matrix are given in the work.

给出了检验疏失误差是否存在的符号检验法和游程数检验法。并给出了存在疏失误差时如何调整实验数据协方差矩阵的方法。

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He believes that black Americans made a great historical error in the 1960s when they relaxed their campaign for civil rights and integration at the first sign of progress, turning their back in many cases on the "blacks only" hotels and restaurants which had sustained them during segregation in favour of the businesses which were newly opening to them.

BBC: Black Washington looks to Obama