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Note 6 - Inventories (Tables)
6 Months Ended
Sep. 30, 2018
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
   
Sept. 30,
2018
   
March 31,
2018
 
Raw materials
  $
1,103,638
    $
1,084,030
 
Work in process
   
1,871,388
     
1,828,492
 
Finished goods
   
600,937
     
737,917
 
Total inventories
  $
3,575,963
    $
3,650,439