We now construct a class of signed invertible graphs, and obtain the condition of equivalence of their signed inverse graphs′being balanced graphs.

构造了一类符号可逆图，并给出了这类图的符号逆图是平衡图的充要条件。

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An almost equal number of males has signed up, but those who actually turn up to class are much fewer than their female counterparts.

报名的男学员也差不多有30人，但来上课的男学员数量比女学员少得多。

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NASA's newest class of astronauts signed up knowing there'd be no U.S. rockets to launch them into space, at least not in the immediate future.

NASA的最新宇航员被告知并不会有美国的火箭送他们进入太空，至少短期内是这样的。

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The justices also questioned whether an arbitrator had the power to bind thousands of absent class members, each of whom had signed their own arbitration agreements, to a class action when they might not want to belong to one.

FORBES: Supreme Court Shows Skepticism About Class Arbitration

For more than 40 years Europe's political class has signed up to the narrative of "ever-closer union".

BBC: Fear in Europe as eurozone crisis deepens

Shane Rector, the highly-regarded point guard who was the cornerstone of former coach Mike Rice's recruiting class, signed with Missouri.

WSJ: Rutgers coach Eddie Jordan is a man on the run