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: Akathisia was defined as either a spontaneous report of restlessness or agitation or a change of 2 or more in the patient - reported akathisia rating scale and a change of at least 1 in the investigator - observed akathisia rating scale .
### Output Text:
Akathisia was defined as either a spontaneous report of restlessness or agitation or a change of 2 or more in the patient - reported akathisia rating scale and a change of at least 1 in the investigator - observed akathisia rating scale . 