group, for example N-[3-[5-(4-fluorophenylthio)-furyl]-2-cyclopenten-1-yl]N-hydroxyurea; R2 is H or an alkyl group having 1 to 4 carbons and R3 is H; X is H or a cation. [0067] Other suitable hydroxyureas are disclosed in, e.g., U.S. Pat. No. 4,299,778, wherein R1 is a phenyl group substituted with one or more fluorine atoms; R2 is a cyclopropyl group; and R3 and X is H. [0068] Other suitable hyd