We discuss the concept of Cremona contractible plane curves, with a historical account on the development of this subject. Then we classify Cremona contractible unions of lines in the plane.
"On the Cremona contractibility of unions of lines in the plane." Kyoto J. Math. 57 (1) 55 - 78, April 2017. https://doi.org/10.1215/21562261-3759513