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 risk of developing renal papillary necrosis or cancer of the renal pelvis , ureter or bladder associated with consumption of either phenacetin or paracetamol was calculated from data acquired by questionnaire from 381 cases and 808 controls .
### Output Text:
The risk of developing renal papillary necrosis or cancer of the renal pelvis , ureter or bladder associated with consumption of either <span class="chemical">phenacetin</span> or <span class="chemical">paracetamol</span> was calculated from data acquired by questionnaire from 381 cases and 808 controls . 