| 1 | The problem is akin to what happened in early set theory. | |
| 2 | The problem is akin to what happened in early set theory. | |
| 3 | There are contradictions in current theories of real number and ZFC. | |
| 4 | In classical set theory, an ordinary set is a unified whole which is composed of some elements. | |
| 5 | Because of the distinctness and broadness of the concept of knowledge set theory, it does not disclose the essence of libraries. |