There has been speculation as to whether the rotor wirings could have been solved without the documents supplied by French Intelligence. Rejewski recalled in 1980 that another way had been found that could have been used to solve the wirings, but that the method was "imperfect and tedious" and relied on chance. In 2005, mathematician John Lawrence claimed that it would have taken four years for this method to have had a reasonable likelihood of success. Rejewski had earlier written that "the conclusion is that the intelligence material furnished to us should be regarded as having been decisive to solution of the machine."