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\proof[size="4,6,8,10,12,14,16,18,20",filename=LibertinusSerif-Regular.otf,heading="Libertinus Serif"]{Fox dwarves, chop my talking quiz job.}
\proof[size="4,6,8,10,12,14,16,18,20",filename=LibertinusSerif-Bold.otf,heading="Libertinus Serif Bold"]{Fox dwarves, chop my talking quiz job.}
\proof[size="4,6,8,10,12,14,16,18,20",filename=LibertinusSerif-Italic.otf,heading="Libertinus Serif Italic"]{Fox dwarves, chop my talking quiz job.}
\proof[size="4,6,8,10,12,14,16,18,20",filename=LibertinusSerif-BoldItalic.otf,heading="Libertinus Serif Bold Italic"]{Fox dwarves, chop my talking quiz job.}
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