-Symbols of unknown quantities, letters representing variables, variable symbols and symbols representing points, line segments and arcs are in white italics; Vector, tensor and matrix symbols are italicized in black; Bold is a special set of symbols; Other symbols and numerical codes are white.

-the equal sign "=" means equal to or approximately equal to "material", not equal to "≦" and greater than ">" and less than ".

-greater than or equal to the symbol "≥" and less than or equal to the symbol "≤".

-Infinite symbol "∞", infinitesimal symbol "-∞".