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: Degenerating myelinated fibers were also evident in distal levels of the peripheral nerves of chickens given TOTP or DFP .
### Output Text:
Degenerating myelinated fibers were also evident in distal levels of the peripheral nerves of chickens given <span class="chemical">TOTP</span> or <span class="chemical">DFP</span> . 