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: Grade 3 - 4 adverse effects included myelosuppression , fatigue , somnolence / depressed mood , neuropathy and dyspnea .
### Output Text:
Grade 3 - 4 adverse effects included myelosuppression , fatigue , somnolence / depressed mood , neuropathy and dyspnea . 