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 univariate matched odds ratio for stroke in women who admitted to using cocaine and / or amphetamine was 8 . 5 ( 95 % confidence interval = 3 . 6 - 20 . 0 ) .
### Output Text:
The univariate matched odds ratio for stroke in women who admitted to using <span class="chemical">cocaine</span> and / or <span class="chemical">amphetamine</span> was 8 . 5 ( 95 % confidence interval = 3 . 6 - 20 . 0 ) . 