Almost all of scholars only studied the possible appearance or disappearance of a limit cycle surrounding a singular Point.
几乎所有的学者只针对极限环内含奇点的情况，讨论了极限环的存在性、唯一性、稳定性以及如何产生与消失。
2
The time of the appearance and disappearance of the strike point at the target is in agreement with the signals measured by the static electric probes.
However, experts point out that the disappearance of HIV patients is not known yet, whether by bone marrow transplantation in the treatment of AIDS is still uncertain.