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: Intracavitary chemotherapy ( paclitaxel / carboplatin liquid crystalline cubic phases ) for recurrent glioblastoma - - clinical observations .
### Output Text:
Intracavitary chemotherapy ( <span class="chemical">paclitaxel</span> / <span class="chemical">carboplatin</span> liquid crystalline cubic phases ) for recurrent glioblastoma - - clinical observations . 