Aging analysis of accounts receivable, net of allowance for impairment loss of doubtful accounts is as follows:
| As of | As of | |||||||
| December 31, 2017 |
December 31, 2016 |
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| Million | Million | |||||||
|
Within 30 days |
13,711 | 10,974 | ||||||
|
31 - 60 days |
3,002 | 2,726 | ||||||
|
61 - 90 days |
1,798 | 1,540 | ||||||
|
Over 90 days |
5,642 | 3,805 | ||||||
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|
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| 24,153 | 19,045 | |||||||
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