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 effectiveness of chronic but not repeated , intermittent injections of CBZ suggests that different biochemical consequences result from the different treatment regimens .
### Output Text:
The effectiveness of chronic but not repeated , intermittent injections of <span class="chemical">CBZ</span> suggests that different biochemical consequences result from the different treatment regimens . 