Source of Engine Pictures & Drawings

I recently watched Oceanliner Design's video about the powerplant and was awestruck by the amount and quality of pictures he and his team managed to find. I also know from posts on this forum that high quality and high detail drawings like this exist of Britannics engine. Can anybody tell me the source of the pictures and drawings?
I know that the website HMHS Britannic has drawings similar to the one in the linked post, but they are comparatively lower quality and apparently much more limited in number, so I am looking for the original source. When it comes to Mike Brady's video, I am especially interested in pictures of the engine during Britannic's fitting out, just like the ones he shows in his video. I'll happily pay for books etc. if that is the only way to get these high quality images.
 
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