- Scientists Want to Know If Earth Once Harbored a Pre-Human Industrial Civilization https://finance.yahoo.com/news/scientists-want-know-earth-once-185200826.html 190 comments aliens
- Scientists want to know if Earth once harbored a pre-human industrial civilization https://www.scientificamerican.com/article/could-an-industrial-prehuman-civilization-have-existed-on-earth-before-ours/ 88 comments science