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: DESIGN : We studied the relation between vitamin C intake and mortality from total cardiovascular disease ( n = 281 ) , coronary artery disease ( n = 175 ) , and stroke ( n = 57 ) in 1923 postmenopausal women who reported being diabetic at baseline .
### Output Text:
DESIGN : We studied the relation between <span class="chemical">vitamin C</span> intake and mortality from total cardiovascular disease ( n = 281 ) , coronary artery disease ( n = 175 ) , and stroke ( n = 57 ) in 1923 postmenopausal women who reported being diabetic at baseline . 