In the field of microbiology, the board, in T 576/91, conceded that an unwritten rule may exist within the scientific community, whereby biological material referred to in a scientific publication can be freely exchanged. However, this does not amount to an obligation, so that any biological material which is the subject of a publication can be considered as being publicly available. The board further stated that if contractual obligations between parties resulted in access to biological material being deliberately restricted to a group of persons bound either by a research contract or a licence, it could not be concluded that this material had been made "available to the public" within the meaning of Art. 54(2) EPC 1973. In T 128/92 the board stated that, for a complex biochemical to be made available to the public, the minimum that would seem to be required for publication was a notice to those in the field that samples of the biochemical could be obtained on request, and clear evidence of exactly what the biochemical was.