David Coupier, Viet-Chi Tran. The 2D-directed spanning forest is almost surely a tree. Random Struct. Algorithms, 42(1):59-72, 2013. [doi]
@article{CoupierT13,
title = {The 2D-directed spanning forest is almost surely a tree},
author = {David Coupier and Viet-Chi Tran},
year = {2013},
doi = {10.1002/rsa.20400},
url = {http://dx.doi.org/10.1002/rsa.20400},
researchr = {https://researchr.org/publication/CoupierT13},
cites = {0},
citedby = {0},
journal = {Random Struct. Algorithms},
volume = {42},
number = {1},
pages = {59-72},
}