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5. Patents (Tables) | 12 Months Ended
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Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract] |
Schedule of intangible assets |
|  | 2019 |  |  | 2018 |
Gross carrying amount - patents |  | $ | 330,588 |  |  | $ | 326,167 |
Accumulated amortization - patents(1) |  |  | (322,774 | ) |  |  | (319,580 | )
Patents, net |  | $ | 7,814 |  |  | $ | 6,587 |
(1) Includes patent impairment charges for the applicable periods.

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