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The secondary source of time series data drawn from various issues has been used.

The effective teacher of history will need to use both primary and secondary sources.

Secondary sources are the works of other historians who have written history.

The author uses mostly secondary sources and comes up with nothing particularly new.

When added to military and secondary sources, the resources could be stretched to 72 years.

A summary of the book within a review is a secondary source.

This secondary source had seemed to be almost impossible to block access to.

Other secondary sources include commercial vendors of oil and gas data.

The Internet is growing as a secondary source for election news, a survey made public yesterday says.

Her fate beyond that date is not reported in secondary sources.