@article{10_4064_ap89_1_1,
     author = {W. M. Mikulski},
     title = {On the variational calculus in fibered-fibered manifolds},
     journal = {Annales Polonici Mathematici},
     pages = {1--12},
     publisher = {mathdoc},
     volume = {89},
     number = {1},
     year = {2006},
     doi = {10.4064/ap89-1-1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap89-1-1/}
}