On read-once vs. multiple access to randomness in logspace

In the correct definition of randomized space-bounded computation, the machine has access to a random coin. The coin can be flipped at will, but outcomes of previous coin flips cannot be recalled unless they are saved in the machine´s limited memory. In contrast to this read-once mechanism of accessing the random source, one may consider Turing machines which have access to a random tape. Here, the random bits may be multiply accessed by the machine. The author demonstrates a very concrete sense in which multiple access to the random bits is better than read-once access to them: Every language accepted with bounded two-sided error by a read-once-randomized logspace machine can be accepted with zero error by a randomized logspace machine having multiple access to the random bits