Gravar-mail: Crystal structures of the Schiff base derivatives (E)-N′-[(1H-indol-3-yl)methyl­idene]isonicotino­hydrazide ethanol monosolvate and (E)-N-methyl-2-[1-(2-oxo-2H-chromen-3-yl)ethyl­idene]hydrazinecarbo­thio­amide