@article{CM_1970__22_2_175_0,
     author = {Takens, Floris},
     title = {The {Lusternik-Schnirelman} categories of a product space},
     journal = {Compositio Mathematica},
     pages = {175--180},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {22},
     number = {2},
     year = {1970},
     mrnumber = {290365},
     zbl = {0198.28302},
     language = {en},
     url = {http://archive.numdam.org/item/CM_1970__22_2_175_0/}
}