The phrase "a substantial and important" is correct and usable in written English.
It can be used to emphasize the significance or weight of a particular subject or issue.
Example: "The research findings provide a substantial and important contribution to our understanding of climate change."
Alternatives: "a significant and vital" or "a considerable and essential".
It's strange that such a substantial and important work in Lindberg's output should have gone unheard in this country for almost a decade.
These policy changes are a substantial and important first step in limiting unnecessary and overbroad requests for reporters' information and confidential sources.
Scientists have hailed the genetic modification of mosquitoes that could crash the insect's populations as a "quantum leap" that will make a substantial and important contribution to eradicating malaria.
In a 2003 study that examined (and named) the "Katie Couric Effect," one of the co-authors, Dr. A. Mark Fendrick, who teaches at the University of Michigan, noted that "a celebrity spokesperson, even one without the condition he or she is promoting, can have a substantial and important impact on what the public does" with respect to particular diseases.
This suggests that the bivariate approach used in constructing fit panels may be ignoring a substantial and important aspect of total sample variability.
"If we can get a half or a third of those, it would make a substantial and important array," Jonas says.
Heaney leaves an substantial and important body of work; his poems always had the human touch.
Still, there is a substantial and clinically important outcome gradient from LRTI patients with pneumococcal isolation only to those with concomitant pneumonia and bacteraemia, which is at least in part mediated by higher acute disease severity and inflammation.
Cooperation with Klaus Deissler, who came each year for several years for consultations on a reflecting team model, was substantial and important.
But if you're building something substantial and important, then there should be more people like me that can recognize that, who can look at A versus A prime, and say, 'Hey, A is better because they've done the work, and they'e done something that's going to matter in 15 to 20 years, and they deserve to be rewarded.'".
In 1968 he drafted and gained political acceptance of a Water Resources Councils' regulation changing the discount rate used in planning water projects from a formula based on the coupon rate of government bonds to one based on the yield rate a substantial and important policy change.
