Question: How to get coefficients from expressions

Hello, I'm a newbie in Maple. I just started learning maple and i'm using version 17. I want to know if there is a way in maple to get the coefficients of some variables maybe an example would explain me better. Lets say we have

23x^4 + (12*h)x^2

So my question is that is there a function/method that can allow me to strip the coefficients of x^4 and x^2. Because I have a very long expression and I need the coefficients of the variables therein to populate a matrix.

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