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: Phase II study of carboplatin and liposomal doxorubicin in patients with recurrent squamous cell carcinoma of the cervix .
### Output Text:
Phase II study of <span class="chemical">carboplatin</span> and liposomal <span class="chemical">doxorubicin</span> in patients with recurrent squamous cell carcinoma of the cervix . 