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: Our present study indicated the possible value of MK - 212 and ( - ) - baclofen in the management of clinical myoclonus .
### Output Text:
Our present study indicated the possible value of <span class="chemical">MK - 212</span> and ( - ) - <span class="chemical">baclofen</span> in the management of clinical myoclonus . 