) ISBN 0-08-006604-6* Hydrobiology website Website for Hydrobiology, Aquacultures, Ichthyology, Water purification and Biological Oceanology - Bulgaria.
) ISBN 0-08-006604-6== External links ==*Hydrobiology website Website for Hydrobiology, Aquacultures, Ichthyology, Water purification and Biological Oceanology - Bulgaria.