Common typos: ffm1991dfm1991dff1991dffm991dffm191dffm199sffm1991fffm1991effm1991xffm1991cffm1991rffm1991ddfm1991dgfm1991drfm1991dcfm1991dvfm1991dtfm1991dfdm1991dfgm1991dfrm1991dfcm1991dfvm1991dftm1991dffn1991dffk1991dffj1991dffm2991dffmq991dffmw991dffm1091dffm1891dffm1o91dffm1i91dffm1901dffm1981dffm19o1dffm19i1dffm1992dffm199qdffm199wfdfm1991dfmf1991dff1m991dffm9191dffm1919sdffm1991dsffm1991fdffm1991dfffm1991edffm1991deffm1991xdffm1991dxffm1991cdffm1991dcffm1991rdffm1991drffm1991ddffm1991dfdfm1991dgffm1991dfgfm1991dfrfm1991dfcfm1991dvffm1991dfvfm1991dtffm1991dftfm1991dffdm1991dffgm1991dffrm1991dffcm1991dffvm1991dfftm1991dffnm1991dffmn1991dffkm1991dffmk1991dffjm1991dffmj1991dffm21991dffm12991dffmq1991dffm1q991dffmw1991dffm1w991dffm10991dffm19091dffm18991dffm19891dffm1o991dffm19o91dffm1i991dffm19i91dffm19901dffm19981dffm199o1dffm199i1dffm19921dffm19912dffm199q1dffm1991qdffm199w1dffm1991wdffmm1991dffm11991dffm19991dffm19911