Question about "spike" & "level shift" anomalies in adtk

[MingZhao2019]

Hi,
I am a researcher who major in anomaly detection in communication field, and I recently read the docs of your developed python library adtk, about spike and level shift anomalies at https://adtk.readthedocs.io/en/stable/userguide.html#spike-and-level-shift. I am sincerely interested in the ‘spike’ and ‘level shift’ anomalies, and I want to study them in a more academical manner, could you please help me?
Actually in some situations in the communication field, anomalies in the time series are very common, and some perform like ‘spike’ and ‘level shift’ anomalies, as you have descripted in the figures at https://adtk.readthedocs.io/en/stable/userguide.html#spike-and-level-shift . I am not sure if there are more references about ‘spike’ and ‘level shift’ so I can study them, including their definitions, behaviors, formulation reasons in concrete fields, and so on. And if not, are ‘spike’ and ‘level shift’ defined by you in your work? I want to know if you have published papers or thesis about them so I can cite them when I finished my study on this topic in the coming future. If not, maybe I can only cite it as “[online] https://adtk.readthedocs.io/en/stable/userguide.html#spike-and-level-shift”.
If it is convenient, I look forward to your reply. Thank you very much!