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: Coronary aneurysm after implantation of a paclitaxel - eluting stent .
### Output Text:
Coronary aneurysm after implantation of a <span class="chemical">paclitaxel</span> - eluting stent . 