TOPIC: Communication time should be spent by a PM as opined by Harold Kirchner

Dear Forum

Client ID: 10942955, Account ID: 799293

In the audio file in one lesson concerning EEF, Cornelius F. referred to Harold Kirchner (spelling might be incorrect, since I have written from his pronunciation) who opined/stated that a PM should/need to spend 90% of his time. I would like to get this proper reference about this time-spent as suggested/opined by Harold Kirchner (any article, website etc so that I can read about much), meaning I would like to get the root source regarding this. I would be happy if any moderator kindly answer to my query.
Many thanks.
M. A. S. Sikder
(a PMP aspirant)