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 condition is treated with intravenous thyroxine ( T4 ) or intravenous tri - iodo - thyronine ( T3 ) .
### Output Text:
The condition is treated with intravenous <span class="chemical">thyroxine</span> ( <span class="chemical">T4</span> ) or intravenous <span class="chemical">tri - iodo - thyronine</span> ( <span class="chemical">T3</span> ) . 