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: Lamivudine is a novel 2 ' , 3 ' - dideoxy cytosine analogue that has potent inhibitory effects on hepatitis B virus replication in vitro and in vivo .
### Output Text:
<span class="chemical">Lamivudine</span> is a novel <span class="chemical">2 ' , 3 ' - dideoxy cytosine</span> analogue that has potent inhibitory effects on hepatitis B virus replication in vitro and in vivo . 