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: METHODS : The authors interviewed six persons with ifosfamide - induced hallucinations in the presence of a clear sensorium .
### Output Text:
METHODS : The authors interviewed six persons with <span class="chemical">ifosfamide</span> - induced hallucinations in the presence of a clear sensorium . 