Persecutory delusions regarding surveillance are a well-documented and recognized clinical feature of schizophrenia and related psychotic disorders, making this common knowledge that requires no citation.
The claim that schizophrenia symptoms frequently involve delusions related to mass surveillance describes a widely recognized, textbook clinical presentation of persecutory delusions in psychiatry. Persecutory and paranoid beliefs concerning being watched, followed, or monitored by external agencies or technology are core features of the disorder described in diagnostic manuals. Therefore, this is common knowledge and requires no citation of specific papers.