Rádl, Stanislav: Syntheses of 1,2, and 9-methyl derivatives of 4,9-dihydro-6-methoxy-3-methyl-4-oxo-1h(2h)-pyrazolo-/3,4-b/quinoline and 4,9-dihydro-6-hydroxy-3-methyl-4-oxo-1h(2h)-pyrazolo/3,4-b/quinoline and their antiviral activity