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: Myocardial catecholamines were also determined in 14 subjects ; a weak correlation ( r = 0 . 57 , P less than 0 . 05 ) between the tissue concentrations of VIP and norepinephrine was noted . ( ABSTRACT TRUNCATED AT 250 WORDS )
### Output Text:
Myocardial <span class="chemical">catecholamines</span> were also determined in 14 subjects ; a weak correlation ( r = 0 . 57 , P less than 0 . 05 ) between the tissue concentrations of VIP and <span class="chemical">norepinephrine</span> was noted . ( ABSTRACT TRUNCATED AT 250 WORDS ) 