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 minimum effective plasma concentrations of ( - ) - cibenzoline for digitalis - and adrenaline - induced arrhythmia were 0 . 06 + / - 0 . 04 and 0 . 7 + / - 0 . 1 micrograms / ml , respectively ( mean + / - SD , n = 6 ) .
### Output Text:
The minimum effective plasma concentrations of ( - ) - <span class="chemical">cibenzoline</span> for <span class="chemical">digitalis</span> - and <span class="chemical">adrenaline</span> - induced arrhythmia were 0 . 06 + / - 0 . 04 and 0 . 7 + / - 0 . 1 micrograms / ml , respectively ( mean + / - SD , n = 6 ) . 