The basic concept and simple application of flex elastic expansion and contraction in HTML, HTML and CSS display: flex; strengthen the understanding of specific usage and use - Programmer Sought
Aligning Items in a Flex Container - CSS: Cascading Style Sheets | MDN
CSS Gap Space with Flexbox
Fill remaining vertical space with CSS using display:flex - Stack Overflow
Cross-browser issues with Flexbox - fastfwd
Aligning Items in a Flex Container - CSS: Cascading Style Sheets | MDN