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: Within the same timeframe , no L - W rat developed a similar palpable PA when treated only with TP .
### Output Text:
Within the same timeframe , no L - W rat developed a similar palpable PA when treated only with <span class="chemical">TP</span> . 