Brace -- from Wolfram MathWorld

GraphicsBrace Wolfram Function Repository

Mathematica Cookbook, PDF, Parallel Computing

Diagonal - Wikipedia

WolframAlpha Full Results API Reference

Structure -- from Wolfram MathWorld

How to solve equations in Wolfram Mathematica - Quora

The PEMDAS Paradox

Brace -- from Wolfram MathWorld

Sets & Set Theory – Mathematical Mysteries

Mathematica Cookbook, PDF, Parallel Computing

Can Mathematica show me step by step solutions? - Quora