The authenticity of an earlier anecdote of a windmill involving the second caliph PERSON@1 -LRB- AD NUMBER@1 NUMBER@2 -RRB- is questioned on the grounds that it appears in a 10th-century document .

The authenticity of an earlier anecdote of a windmill involving the second caliph PERSON@1 -LRB- NUMBER@3 AD -RRB- is questioned on the grounds of being a 10th century amendment .
