The mechanism of liquid wicking upward in porous materials such as paper towels via capillary action is a fundamental, everyday physical observation that does not require formal academic citations.
The claim describes well-established physical principles of capillary action and surface wetting in porous substrates, which represent common knowledge. While some retrieved papers discuss liquid penetration in sprays or microfluidic wicking (e.g., paper-based microfluidics and spontaneous imbibition), none of them are required to substantiate this basic physical fact.