Abd al-Raḥmān ibn Abi-Bakr Siyuṭi [Deceased in 911AH], started his book “Al-Ḥāwī Lilfatāwā” with these sentences:

‘It’s a chapter, in which I collected the hadiths and traditions about Mahdī (mgehr)

I briefly mentioned, the forty hadiths that “Hāfiz Abu Na’īm” had presented.

In addition, I added and encoded in “K” whatever he hadn’t mentioned.

[Well], the whole hadiths that were collected in this book_ both narrated and added by Abu Na’īm_ are more than two hundred hadiths…

Siyuṭi, I. J. “Al-Ḥāwī Lilfatāwā”, P.69

Khoda Morad Salimian, I. J. “Darsname Mahdaviat”, Vol.1, P.78