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		<text> 0</text>
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	<g transform="translate(59,275)" 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(59,210)" style="stroke:none; fill:black; font-family:sans-serif; font-size:12.00; text-anchor:end">
		<text> 10</text>
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		<text> 15</text>
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		<text> 20</text>
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		<text> 25</text>
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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> 2000</text>
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		<text>Number of references</text>
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		<text>Year of publication</text>
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