@article{DOCMA_2009__14__a21,
     author = {Lenz, Daniel and Stollmann, Peter and Veseli\'c, Ivan},
     title = {The {Allegretto-Piepenbrink} theorem for strongly local {Dirichlet} forms},
     journal = {Documenta mathematica},
     pages = {167--189},
     publisher = {mathdoc},
     volume = {14},
     year = {2009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DOCMA_2009__14__a21/}
}