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: METHODS : Six groups of 6 BALB / c mice were treated with saline , DOX alone or DOX ( 4 mg / kg i . v . ) preceded by monoHER ( 500 mg / kg i . p . ) with an interval of 10 , 30 , 60 or 120 min .
### Output Text:
METHODS : Six groups of 6 BALB / c mice were treated with saline , <span class="chemical">DOX</span> alone or <span class="chemical">DOX</span> ( 4 mg / kg i . v . ) preceded by <span class="chemical">monoHER</span> ( 500 mg / kg i . p . ) with an interval of 10 , 30 , 60 or 120 min . 