Volume 6, Issue 2 John R. Graef Shapour Heidarkhani Lingju Kong Nontrivial solutions for systems of Sturm-Liouville boundary value problems Downloads Abstract PDF Full article PDF DOI { copied = true; setTimeout(() => copied = false, 2000) })" :aria-label="copied ? 'DOI copied' : 'Copy DOI'" :title="copied ? 'Copied' : 'Copy DOI'" > Find all available articles from these authors John R. Graef Shapour Heidarkhani Lingju Kong Find more articles with the same keywords nontrivial solutions Sturm-Liouville boundary conditions critical point theory Find more articles with the same subject classes 34B15 47J10