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: Chickens given 200 ppm corticosterone without TOTP or DFP had significantly elevated activity of plasma cholinesterase and significantly inhibited activity of liver carboxylesterase .
### Output Text:
Chickens given 200 ppm <span class="chemical">corticosterone</span> without <span class="chemical">TOTP</span> or <span class="chemical">DFP</span> had significantly elevated activity of plasma cholinesterase and significantly inhibited activity of liver carboxylesterase . 