00356    a2200133   4500082001600000100001900016245005300035250000900088260004700097300002200144650002700166650001600193650001300209  a515.35bCOH  aCohen, Abraham  aAn elementary treatise on differential equations  a2nd.  aBostonbD.C. Heath and companyc1933g1933  avii, 337p.c20cm.  aDIFFERENTIAL EQUATIONS  aMATHEMATICS  aANALYSIS