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		<text> 0</text>
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	<g transform="translate(59,286)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 10</text>
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		<text> 20</text>
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		<text> 30</text>
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		<text> 40</text>
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		<text> 50</text>
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	<g transform="translate(59,13)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 60</text>
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<g style="fill:none; color:gray; stroke:currentColor; stroke-width:0.20">
	<path d='M188,337 L188,9 '></path>
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		<text> 1960</text>
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		<text> 1970</text>
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		<text> 1980</text>
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		<text> 1990</text>
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		<text>Number of references</text>
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		<text>Year of publication</text>
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