Y. H. Ahn, K. S. Min, and Z. Yun, Enhancement of reactor performance and pelletization by reactor modification in UASB system, Journal of Environmental Science and Health, Part A, vol.31, issue.12, pp.1719-1733, 2000.
DOI : 10.1007/BF00549357

G. S. Geeta, K. S. Jagadeesh, and T. K. Reddy, Nickel as an accelerator of biogas production in water hyacinth (Eichornia crassipes solms.), Biomass, vol.21, issue.2, pp.157-161, 1990.
DOI : 10.1016/0144-4565(90)90056-P

S. K. Goyal, R. Srth, and B. K. Handa, Diphasic fixed-film biomethanation of distillery spentwash, Bioresource Technology, vol.56, issue.2-3, pp.239-244, 1996.
DOI : 10.1016/0960-8524(96)00033-8

S. S. Kanwar, R. L. Guleri, . Biotechnol, . Biotechnol, and . Eq, Biogas Forum IV, SE SECOND BALKAN CONFERENCE ON BIOLOGY SPECIAL EDITION, vol.566, issue.24, pp.12-13, 1994.

D. Karamanev and L. Nikolov, A comparison between the reaction rates in biofilm reactors and free suspended cells bioreactors, Bioprocess Engineering, vol.6, issue.3, pp.127-130, 1991.
DOI : 10.1007/BF00369066

L. Nikolov, Scientific Session ? 60 Years The Stephan Angelov Institute of Microbiology, Associated with Institut Pasteur ? oral presentation, Program and Abstracts, p.17, 2007.

L. Nikolov, Automatics and Informatics " '08, John Atanassov celebration days, PROCEEDINGS of the International Conference, 2008.

L. Nikolov and D. Karamanev, Experimental study of the inverse fluidized bed biofilm reactor, The Canadian Journal of Chemical Engineering, vol.6, issue.2, pp.214-217, 1987.
DOI : 10.1002/cjce.5450650204

L. Nikolov and D. Karamanev, In: Physiology of immobilized cells, J.A.M. DeBont et all, pp.461-466, 1990.

V. Mamatarkova, L. Nikolov, and D. Karamanev, Part I, Biotechnol. Biotechnol. Eq. Part II, Biotechnol. Biotechnol. Eq, vol.16, issue.16, pp.172-176, 2002.

W. Parawira, M. Murto, R. Zvauya, and B. Mattiasson, Anaerobic batch digestion of solid potato waste alone and in combination with sugar beet leaves, Renewable Energy, vol.29, issue.11, pp.1811-1823, 2004.
DOI : 10.1016/j.renene.2004.02.005

E. Sanchez, S. Montalvo, L. Travieso, and X. Rodriguez, Anaerobic digestion of sewage sludge in an anaerobic fixed bed digester, Biomass and Bioenergy, vol.9, issue.6, pp.493-495, 19950.
DOI : 10.1016/0961-9534(95)00038-0

D. K. Sharma, Center for Rural Development and Technology, Indian Institute of technology, 2002.

S. P. Singh and P. Prerna, Review of recent advances in anaerobic packed-bed biogas reactors, Renewable and Sustainable Energy Reviews, vol.13, issue.6-7, pp.1569-1575, 2009.
DOI : 10.1016/j.rser.2008.08.006

D. Somayaji and S. Khana, Biomethanation of rice and wheat straw, World Journal of Microbiology & Biotechnology, vol.11, issue.5, pp.521-523, 1994.
DOI : 10.1007/BF00367657

N. Takiguchi, M. Kishino, A. Kuroda, J. Kato, and H. Ohtake, A laboratory-scale test of anaerobic digestion and methane production after phosphorus recovery from waste activated sludge, Journal of Bioscience and Bioengineering, vol.97, issue.6, pp.365-368, 2004.
DOI : 10.1016/S1389-1723(04)70219-4

S. Tirumale and K. Nand, Biogas Forum III, pp.12-15, 1994.

D. Trujillo, J. F. Perez, and F. J. Cerebros, Energy recovery from wastes. Anaerobic digestion of tomato plant mixed with rabbit wastes, Bioresource Technology, vol.45, issue.2, pp.81-83, 1993.
DOI : 10.1016/0960-8524(93)90093-Q

M. H. Wong and Y. H. Cheung, Gas production and digestion efficiency of sewage sludge containing elevated toxic metals, Bioresource Technology, vol.54, issue.3, pp.261-268, 1995.
DOI : 10.1016/0960-8524(95)00139-5

S. Yadvika, T. R. Sreekrishnan, S. Kohli, and V. Rana, Enhancement of biogas production from solid substrates using different techniques??????a review, Bioresource Technology, vol.95, issue.1, pp.1-10, 2004.
DOI : 10.1016/j.biortech.2004.02.010