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5. Patents (Tables)
12 Months Ended
Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]  
Schedule of intangible assets
   2020   2019 
Gross carrying amount - patents  $336,834   $330,588 
Accumulated amortization - patents(1)   (319,922)   (322,774)
Patents, net  $16,912   $7,814