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: CONCLUSION : This case started with a media report in a popular newspaper , initiated by published , peer - reviewed research on herbals , and involved human failure in a case history , medical examination and clinical treatment .
### Output Text:
CONCLUSION : This case started with a media report in a popular newspaper , initiated by published , peer - reviewed research on herbals , and involved human failure in a case history , medical examination and clinical treatment . 