  Csisz\'ar's channel coding theorem for multiple codebooks is generalized
allowing the codeword lenghts differ across codebooks. Also in this case, for
each codebook an error exponent can be achieved that equals the random coding
exponent for this codebook alone, in addition, erasure detection failure
probability tends to 0. This is proved even for sender and receiver not knowing
the channel. As a corollary, a substantial improvement is obtained when the
sender knows the channel.
