Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:FEBS Lett 486:173-177 Peitsch MC (1995) Protein Modeling by E-Mail (Vol 13, Pg 658, 1995). Bio-Technology 13:723-723 Ravichandran KG, Boddupalli SS, Hasermann CA, Peterson JA, Deisenhofer J (1993) Crystal structure of hemoprotein domain of P450BM-3, a prototype for microsomal P450's. Science 261:731-736 Salazar O, Cirino PC, Arnold FH (2003) Thermostabilization of a Cytochrome P450 Peroxygenase. Chembiochem 4:891-893 Sallam L, Naim N, Zeinel-Abdin Badr A, El-Refai A (1977) Bioconversion of progesterone with cell preparations with Aspergillus niger 171. Rev Latinoam Microbiol 19:151153 Schwaneberg U, Schmidt-Dannert C, Schmitt J, Schmid RD (1999) A continuous spectrophotometric assay for P450 BM-3, a fatty acid hydroxylating enzyme, and its mutant F87A. Anal Biochem 269:359-366 Schwede T, Kopp J, Guex N, Peitsch MC (2003) SWISS-MODEL: An automated protein homology-modeling server. Nucleic Acids Res 31:3381-3385 Seng Wong T, Arnold FH, Schwaneberg U (2004) Laboratory evolution of cytochrome p450 BM-3 monooxygenase for organic cosolvents. Biotechnol Bioeng 85:351-358 Wen LP, Fulco AJ (1987) Cloning of the gene encoding a catalytically self-sufficient cytochrome P-450 fatty acid monooxygenase induced by barbiturates in Bacillus megaterium and its functional expression and regulation in heterologous (Escherichia coli) and homologous (Bacillus megaterium) hosts.
Category: