PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, cilt.129, sa.5, ss.1545-1549, 2001 (SCI-Expanded)
There exists a (relatively minimal) genus g Lefschetz fibration with only one singular fiber over a closed (Riemann) surface of genus h iff g greater than or equal to 3 and h greater than or equal to 2. The singular fiber can be chosen to be reducible or irreducible. Other results are that every Dehn twist on a closed surface of genus at least three is a product of two commutators and no Dehn twist on any closed surface is equal to a single commutator.