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: Bortezomib ( bort ) - dexamethasone ( dex ) is an effective therapy for relapsed / refractory ( R / R ) multiple myeloma ( MM ) .
### Output Text:
<span class="chemical">Bortezomib</span> ( <span class="chemical">bort</span> ) - <span class="chemical">dexamethasone</span> ( <span class="chemical">dex</span> ) is an effective therapy for relapsed / refractory ( R / R ) multiple myeloma ( MM ) . 