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: METHODS : In October , 1992 , we started a double - blind placebo - controlled , randomised trial of tamoxifen in women ( mainly in Italy ) who did not have breast cancer and who had had a hysterectomy .
### Output Text:
METHODS : In October , 1992 , we started a double - blind placebo - controlled , randomised trial of <span class="chemical">tamoxifen</span> in women ( mainly in Italy ) who did not have breast cancer and who had had a hysterectomy . 