Christian Louboutin's Red Shoe Soles are a valid Trademark.
Europe top court rules should not sell third party knock-off Louboutin shoes
Red Sole Imitators - Zara Defeats Loubouton In Trademark Case
Louboutin could lose red-sole monopoly
Christian Louboutin on Cardi B and His 'Red Bottoms' - The New York Times
Christian Louboutin scrambles to trademark his red-soled shoes
Position trademark and shape trademark: the Louboutin case - Canella Camaiora
WWD Law Review: Louboutin Fights On, Hacking Woes and Italian Taxes – WWD
Louboutin's new red sole woe - Telegraph