@article {2021,
	title = {Non-well-ordered lower and upper solutions for semilinear systems of PDEs},
	journal = {Communications in Contemporary MathematicsCommunications in Contemporary Mathematics},
	year = {2021},
	month = {2021/08/27},
	pages = {2150080},
	abstract = {<p>We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.</p>},
	isbn = {0219-1997},
	url = {https://doi.org/10.1142/S0219199721500802},
	author = {Alessandro Fonda and Giuliano Klun and Andrea Sfecci}
}
@article {fonda2011nonlinear,
	title = {Nonlinear resonance: a comparison between Landesman-Lazer and Ahmad-Lazer-Paul conditions},
	journal = {Advanced Nonlinear Studies},
	volume = {11},
	number = {2},
	year = {2011},
	pages = {391{\textendash}404},
	publisher = {Advanced Nonlinear Studies, Inc.},
	abstract = {<p>We show that the Ahmad-Lazer-Paul condition for resonant problems is more general than the Landesman-Lazer one, discussing some relations with other existence conditions, as well. As a consequence, such a relation holds, for example, when considering resonant boundary value problems associated with linear elliptic operators, the p-Laplacian and, in the scalar case, with an asymmetric oscillator.</p>},
	doi = {10.1515/ans-2011-0209},
	author = {Alessandro Fonda and Maurizio Garrione}
}
