@article{DMGAA_2012_32_1_a1,
     author = {Steinby, Magnus},
     title = {On the solidity of general varieties of tree languages},
     journal = {Discussiones Mathematicae. General Algebra and Applications},
     pages = {23--53},
     publisher = {mathdoc},
     volume = {32},
     number = {1},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGAA_2012_32_1_a1/}
}