. . . . "The electron-withdrawing group refers to a group having a plus (+) value as Hammett's substituent constant ?? (???KAGAKU JITEN (Chemical Dictionary)???, pages 833-834, 1986, published by Morikita Shuppan K.K.), and may include, e.g., halogen atoms such as a fluorine atom, a chlorine atom and a bromine atom, a trifluoromethyl group, a trichloromethyl group, a tribromomethyl group, a nitro group, a" . . .