实际上，循环引用也不总是有害的，有时它是完全必需的。
Circular references are not always bad and, in fact, are sometimes absolutely necessary.
比如，复杂的数据关系要求有完全的引用完整性限制。
For instance, complex data relationships would require full referential integrity enforcement.
这个幽默的引用指向一个简单的事实：没有人能完全逃离恐惧。
This humorous quote points to a simple truth: No one can escape fear completely.
有关HTML4中全部的字符实体引用信息，请参阅字符引用完全列表部分。
Please consult the full list of character references defined in HTML 4.
有关HTML4中全部的字符实体引用信息，请参阅字符引用完全列表部分。
Please consult the full list of character references defined in HTML 4.
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