1970/2: Beneath the Planet of the Apes 1970

 Trailer:

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https://archive.org/details/honeymustardvhs/Planet+Of+The+Apes+2+-+Beneath+The+Planet+Of+The+Apes.avi

https://en.wikipedia.org/wiki/Beneath_the_Planet_of_the_Apes

https://www.moriareviews.com/sciencefiction/beneath-the-planet-of-the-apes-1970.htm 

https://eofftvreview.wordpress.com/2020/01/04/beneath-the-planet-of-the-apes-1970/

https://poweredbyrobots.com/2019/09/01/film-review-of-beneath-the-planet-of-the-apes-1970/