@article{700603,
     title = {Countable small rank and cardinal invariants},
     booktitle = {General topology and its relations to modern analysis and algebra IV},
     series = {GDML\_Books},
     publisher = {Society of Czechoslovak Mathematicians and Physicist},
     address = {Praha},
     year = {1977},
     pages = {[344]-347},
     mrnumber = {MR0675591},
     zbl = {0371.54012},
     url = {http://dml.mathdoc.fr/item/700603}
}

Nyikos, P. Countable small rank and cardinal invariants, dans General topology and its relations to modern analysis and algebra IV, GDML_Books,  (1977), pp. [344]-347. http://gdmltest.u-ga.fr/item/700603/