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: Careful observation of patients receiving high - dose MP is recommended .
### Output Text:
Careful observation of patients receiving high - dose <span class="chemical">MP</span> is recommended . 