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 ESRD associated with aspirin was related to the cumulated dose and duration of use , and it was particularly high among the subset of patients with vascular nephropathy as underlying disease [ 2 . 35 ( 1 . 17 - 4 . 72 ) ] .
### Output Text:
The risk of ESRD associated with <span class="chemical">aspirin</span> was related to the cumulated dose and duration of use , and it was particularly high among the subset of patients with vascular nephropathy as underlying disease [ 2 . 35 ( 1 . 17 - 4 . 72 ) ] . 