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: We report mefenamic acid - induced non - oliguric renal failure and severe neutropenia occurring simultaneously in two elderly females .
### Output Text:
We report <span class="chemical">mefenamic acid</span> - induced non - oliguric renal failure and severe neutropenia occurring simultaneously in two elderly females . 