In the newspaper articles they make references to the research. For Example in the first paper from 1975 it is Paul R Erlich who is the researcher.

If you want, you can track down the paper. It may be difficult though.

Edit: In 1968, Dr. Paul R. Ehrlich wrote a well-publicized book entitled The Population Bomb . Ehrlich predicted widespread famine and disaster unless population growth was reduced to zero in America and throughout the world by compulsory methods if necessary.

Edit: https://science.sciencemag.org/content/173/3992/138.abstract