The distinction has not gone unchallenged in both its theoretical and practical implications. (religion-online.org)
Granulated clay litters remained unchallenged for nearly 40 years, with little change or refinement until Thomas Nelson, Ph.D., needed a way to supplement his income while in graduate school. (pets.webmd.com)
Questrade has largely gone unchallenged by other Canadian online brokerages in offering up Apple products as incentives for new account openings. (sparxtrading.com)