12. Intangible assets, net

Amortization expense recognized for the years ended December 31, 2017, 2018 and 2019 are summarized as follows:


	Years ended December 31
(In thousands)	2017	2018	2019
Cost of revenues	241	266	5
General and administrative expenses	415	721	1,136
Research and development expenses	1,445	244	59
Total	2,101	1,231	1,200

The estimated aggregate amortization expense for each of the next five years as of December 31, 2019 is:

The weighted average amortization periods of intangible assets as at December 31, 2018 and 2019 are as below:


(In year)	December 31, 2018	December 31, 2019
Land use right	30	30
Acquired computer software	5	5
Online game licenses	3	3
Audio-visual license	9	9
Total weighted average amortization periods	12	12