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: Studies with long - term lamivudine administration should be performed to determine if prolonged suppression of HBV DNA can be achieved .
### Output Text:
Studies with long - term <span class="chemical">lamivudine</span> administration should be performed to determine if prolonged suppression of HBV DNA can be achieved . 