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		<text> 0</text>
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	<g transform="translate(59,294)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 5</text>
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	<g transform="translate(59,247)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 10</text>
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	<g transform="translate(59,200)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 15</text>
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	<g transform="translate(59,154)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 20</text>
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		<text> 25</text>
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	<g transform="translate(59,60)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 30</text>
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<g style="fill:none; color:black; stroke:currentColor; stroke-width:0.20">
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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> 35</text>
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	<path d='M177,337 L177,9 '></path>
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		<text> 1970</text>
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<g style="fill:none; color:gray; stroke:currentColor; stroke-width:1.00">
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		<text> 1980</text>
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	<path d='M465,337 L465,9 '></path>
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<g style="fill:none; color:gray; stroke:currentColor; stroke-width:1.00">
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<g style="fill:none; color:black; stroke:currentColor; stroke-width:1.00">
	<path d='M465,337 L465,346 M465,9 L465,0 '></path>
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		<text> 1990</text>
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	<path d='M609,337 L609,9 '></path>
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<g style="fill:none; color:gray; stroke:currentColor; stroke-width:1.00">
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<g style="fill:none; color:black; stroke:currentColor; stroke-width:1.00">
	<path d='M609,337 L609,346 M609,9 L609,0 '></path>
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		<text> 2000</text>
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		<text> 2010</text>
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		<text>Number of references</text>
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		<text>Year of publication</text>
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