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: The adverse drug reaction score obtained by the Naranjo algorithm was 6 in our case , indicating a probable relationship between the patient ' s NMS - like adverse symptoms and the combined treatment used in this case .
### Output Text:
The adverse drug reaction score obtained by the Naranjo algorithm was 6 in our case , indicating a probable relationship between the patient ' s NMS - like adverse symptoms and the combined treatment used in this case . 