@phdthesis{UNY2255,
          author = {Amroni Umi},
           title = {MASALAH STRUM-LIOUVILLE SINGULAR DAN APLIKASINYA},
           month = {July},
            year = {2010},
          school = {UNY},
             url = {http://eprints.uny.ac.id/2255/}
}