@article{MM2_1989__65_3_155443,
     author = {Masataka Tomari and Fumio Hidaka},
     title = {On singularities arising from the contraction of the minimal section a a ruled surface.},
     journal = {Manuscripta mathematica},
     pages = {329--348},
     publisher = {mathdoc},
     volume = {65},
     number = {3},
     year = {1989},
     zbl = {0705.14036},
     url = {http://geodesic.mathdoc.fr/item/MM2_1989__65_3_155443/}
}