In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The FK506 plus SRL combination showed only a marginally higher degree of fibrosis as compared with controls ( P = 0 . 05 ) .
### Output Text:
The <span class="chemical">FK506</span> plus <span class="chemical">SRL</span> combination showed only a marginally higher degree of fibrosis as compared with controls ( P = 0 . 05 ) . 