Purwadaria, T., Sinurat, A., Haryati, T., Sutikno, I., Supriyati, & Dharma, J. (1998). The correlation between mannanase and cellulase activities towards fibre content of palm oil sludge fermented with Aspergillus niger. Pusat Penelitian dan Pengembangan Peternakan.

Purwadaria, T., A.P Sinurat, T. Haryati, I. Sutikno, Supriyati, e J. Dharma. The Correlation between Mannanase and Cellulase Activities Towards Fibre Content of Palm Oil Sludge Fermented With Aspergillus Niger. Pusat Penelitian dan Pengembangan Peternakan, 1998.

Purwadaria, T., et al. The Correlation between Mannanase and Cellulase Activities Towards Fibre Content of Palm Oil Sludge Fermented With Aspergillus Niger. Pusat Penelitian dan Pengembangan Peternakan, 1998.