Where to find these filtering operators in Matlab (Kirsh Marks,Robert,LaPlacian)?

Hello.

I took a look at the page: http://www.mathworks.es/help/toolbox/images/ref/edge.html of the documentation but is seems some operator are ""missing".

Specifically I can't find the following:

- Kirsh marks

- Robert

- LaPlacian Filter: I saw you have "log" and "laplacian". But what's the difference?

- Moreover: to apply "Marr-Hildreth" I have to apply first "mean" and then "zerocross". Correct?

Thank you very much in advance.