The one that I found is from May 5,1988
by Professor Stan Lowy Department of Aerospace Engineering Texas A M University
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890008382.pdf
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Sign up to join this communityThe one that I found is from May 5,1988
by Professor Stan Lowy Department of Aerospace Engineering Texas A M University
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890008382.pdf
I found something more recent.
https://phys.org/news/2019-05-lunar-tunnel-moon-colonies.html