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v3.19.3

Summary of significant accounting policies - Employee benefit (Details) - USD ($) | 12 Months Ended
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Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2017
Summary of significant accounting policies |  |  |
Total expense for the plans | $ 95,331 | $ 54,804 | $ 51,801

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration