Solid vs Outline 禄 Welches Icon ist besser zu erkennen?
Hollow Icon vs. Solid Icon: Which Is More Friendly for Recognizing? | by Trista liu | Medium
Solid Vs. Outline Icons: Which Are Faster to Recognize?
Master's Paper | Filled-in vs. Outline Icons: The Impact of Icon Style on Usability
Solid vs. Outline Icons: Which Are Faster to Recognize?
gui design - Can solid and hollow icons be used together? - User Experience Stack Exchange
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