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: In conclusion , the combined administration of BPT / CLZ is safe at doses used in the study , though the beneficial clinical effect of the combined administration has yet to be elucidated .
### Output Text:
In conclusion , the combined administration of <span class="chemical">BPT</span> / <span class="chemical">CLZ</span> is safe at doses used in the study , though the beneficial clinical effect of the combined administration has yet to be elucidated . 