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Use search limiters
Date limiters can help you narrow down results to the relevant time frame
Trade journals (found in Business Source) will be valuable resources
Don't rely solely on the company's websites and press releases
They are not your most objective source
Be sure you are researching the official name of the company. Many companies have popular names that may not be listed anywhere. For example, 3M is really Minnesota Mining and Manufacturing.
If the company is a personal name or includes initials, e.g. Walt Disney or H. J. Heinz, look under each part of the name. Various sources are not consistent in how names are treated.
If you are researching a subsidiary, expand your research to include the parent corporation.
Very small or very new companies may not appear in the standard sources, particularly print sources. Look for news articles and a company website. Use any regional or specialized industry directories which may be available.