2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/14420Three recent papers have been collected here, discussing the possibility and properties of periodic modulation of a signal from accreting black holes surrounded by orbiting clumps of gas.19 pages, 7 figures; LaTeX2.09, contains a collection of three related preprints, to appear in PASJ and ApJAstrophysicstext