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: Forty - two Chinese HBsAg carriers were randomized to receive placebo ( 6 patients ) or lamivudine orally in dosages of 25 mg , 100 mg , or 300 mg daily ( 12 patients for each dosage ) .
### Output Text:
Forty - two Chinese <span class="chemical">HBsAg</span> carriers were randomized to receive placebo ( 6 patients ) or <span class="chemical">lamivudine</span> orally in dosages of 25 mg , 100 mg , or 300 mg daily ( 12 patients for each dosage ) . 