@article{MAN_1989__285_1_164611,
     author = {Chuan-yi Xu},
     title = {The existence of nonclassical asymptotic expansion of the trace of a heat kernel for a degenerate elliptic operator.},
     journal = {Mathematische Annalen},
     pages = {447--462},
     publisher = {mathdoc},
     volume = {285},
     number = {1},
     year = {1989},
     zbl = {0663.35032},
     url = {http://geodesic.mathdoc.fr/item/MAN_1989__285_1_164611/}
}