1) PALLERONI, N. J.; K. E. REICHELT, D. MUELLER, R. EPPS, B. TABENKIN, D. N. BULL, W. SCHÜEP & J. BERGER: Production of a novel red pigment, rubrolone by <i>Streptomyces echinoruber</i> sp. nov. I. Taxonomy, fermentation and partial purification. J. Antibiotics 31: 1218-1225 1978
2) BERGER, J.; K. REICHELT & W. SCHÜEP: Certain pyrano-furo-azulenopyridines. U.S. Patent 4,057,553, Nov. 8, 1977