String sign of Kantor
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Compliance with ethical standards
No funding was received for this study.
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with animals performed by any of the author(s). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.