We do have one, which borrows liberally from the message the DITA TC used, modified for the situation. I further modified it so it will work equally well coming from someone who is not on the DocBook TC.
Thanks,
Dick
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Dear NAME,
I'm writing to ask you, as the OASIS representative for your company, to vote for the DocBook 5.1 standard. The vote is now open and will remain open until Tuesday, November 22, midnight (GMT).
The DocBook standard is a well-established standard for marking up technical documentation. It is widely used in the Linux and open-source community, as well as by major publishers such as O’Reilly Media.
Here is a link to the OASIS page for the vote: https://www.oasis-open.org/apps/org/workgroup/voting/ballot.php?id=3010
The vote itself takes a couple of quick clicks on that page.
If you have any questions about DocBook, you can find links to the proposed standard on the vote page, or you can visit the DocBook OASIS page at: https://www.oasis-open.org/committees/docbook
Thanks very much for your time and consideration. I hope you choose to vote for this standard.
Best regards
YOUR NAME
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