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Copyright © 2019 The Chinese Medical Association, Published by Wolters
Kluwer Health, Inc. under the CCBY-NC-ND license.
This is an open-access article distributed under the terms of the Creative
Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-
ND), where it is permissible to download and share the work provided it is
properly cited. The work cannot be changed in any way or used commercially
without permission from the journal.
Except where otherwise noted, this item's license is described as Copyright © 2019 The Chinese Medical Association, Published by Wolters Kluwer Health, Inc. under the CCBY-NC-ND license. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC- ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.