@article{IM_1988__94_2_143632,
     author = {C.D. Sogge and F.M. Christ},
     title = {The weak type {L1} convergence of eigenfunction expansions for pseudodifferential operators.},
     journal = {Inventiones mathematicae},
     pages = {421--454},
     publisher = {mathdoc},
     volume = {94},
     number = {2},
     year = {1988},
     zbl = {0678.35096},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__94_2_143632/}
}