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: There was no difference in the rate of engraftment of evaluable patients in the two groups ( P greater than 0 . 5 ) .
### Output Text:
There was no difference in the rate of engraftment of evaluable patients in the two groups ( P greater than 0 . 5 ) . 