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 agreement between the questionnaire and tremor severity ( r = 0 . 093 ; P = 0 . 53 ) .
### Output Text:
There was no agreement between the questionnaire and tremor severity ( r = 0 . 093 ; P = 0 . 53 ) . 