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: Laboratory evaluation revealed 66 , 680 U / L creatine kinase , 93 mg / dL blood urea nitrogen , 4 . 6 mg / dL creatinine , 1579 U / L aspartate aminotransferase , and 738 U / L alanine aminotransferase .
### Output Text:
Laboratory evaluation revealed 66 , 680 U / L <span class="chemical">creatine</span> kinase , 93 mg / dL <span class="chemical">blood urea nitrogen</span> , 4 . 6 mg / dL <span class="chemical">creatinine</span> , 1579 U / L <span class="chemical">aspartate</span> aminotransferase , and 738 U / L <span class="chemical">alanine</span> aminotransferase . 