@article{10_4064_fm179_1_6,
     author = {X. Z. Zhao and Y. Q. Guo and K. P. Shum},
     title = {Sturdy frames of type $(2,2)$ algebras
 and their applications to semirings},
     journal = {Fundamenta Mathematicae},
     pages = {69--81},
     publisher = {mathdoc},
     volume = {179},
     number = {1},
     year = {2003},
     doi = {10.4064/fm179-1-6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm179-1-6/}
}