Some time ago, I posted a paper on 'The introduction and development of Category A procedures (from runways to heliports in city centres)'. It was quite well received, but it has now been edited to remove some esoteric items and add illustrations to make it easier on the eyes.
https://www.dropbox.com/scl/fi/as4w9...ff413ixpa&dl=0
The paper was revisited to assist the current ICAO work on the adaptation of Annex 14, Volume II, for the introduction of eVTOL, and the necessity to inform the eVTOL community of the issues associated with the siting of heliports/vertiports in city centres in view of the general public's expectation that these operations will introduce a level of safety equivalent to airline operations.
Jim