The simplest thing is something called a consol or perpetuity.

其中最简单的东西叫做公债或叫永续年金

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There have also been one hundred-year bonds and there have also been perpetuities that-- in the UK, for example, the British Consoles-- have no expiration date and they have infinite maturity.

还有更长期的一百年债券,还有一种永续年金,比如说英国的大英统一公债,没有过期日,永不到期

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