@article{10_4064_fm232_2_6,
     author = {Joan Bagaria and Saharon Shelah},
     title = {On partial orderings having precalibre-$\aleph _1$ and
 fragments of {Martin's} axiom},
     journal = {Fundamenta Mathematicae},
     pages = {181--197},
     publisher = {mathdoc},
     volume = {232},
     number = {2},
     year = {2016},
     doi = {10.4064/fm232-2-6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm232-2-6/}
}