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 possibilities that these cardiovascular findings might be the result of non - selective inhibition of monoamine oxidase or of amphetamine and metamphetamine are discussed .
### Output Text:
The possibilities that these cardiovascular findings might be the result of non - selective inhibition of monoamine oxidase or of <span class="chemical">amphetamine</span> and <span class="chemical">metamphetamine</span> are discussed . 