index subsorting question

[Denis B. Roegel]

\index{A} puts A in the index.

\index[A]{\A} puts \A under A in the index

\index{letter+A} puts the subentry A under the entry letter in the index

This leads to two questions:

  1) how can I put \A with the subentry A under the entry letter in the index?

  2) how can I put \A with the subentry A under the entry \letter 
      (which is itself with letter) in the index?

Thanks,

Denis