Andrzej Pownuk, Luc Longpré, Vladik Kreinovich. Checking Monotonicity is NP-Hard Even for Cubic Polynomials. Reliable Computing, 18:90-96, 2013. [doi]
@article{PownukLK13,
title = {Checking Monotonicity is NP-Hard Even for Cubic Polynomials},
author = {Andrzej Pownuk and Luc Longpré and Vladik Kreinovich},
year = {2013},
url = {http://interval.louisiana.edu/reliable-computing-journal/volume-18/reliable-computing-18-pp-090-096.pdf},
researchr = {https://researchr.org/publication/PownukLK13},
cites = {0},
citedby = {0},
journal = {Reliable Computing},
volume = {18},
pages = {90-96},
}