Yes Nelsonys,
Basic electronics mate, high switching currents bigger problems, 25 years plus doing this job and research, the fact that I do mil and areo designs so my EMC testing is more stringent than comercialso I have seen problems, a desire to do a design to the BEST of my abbilities. and be less abrupt please.
I have had had training on sirte provided by Nation Semiconductor on the layout of switch mode power supplies and the EMC problems they cause, provided by thier . We dont run any copper (including ground tracks) under any switching nodes.
The CE club have lots of notes on switching circuits and noise, in fact Keith Armstrong has a new series that has been running for 3 months.
EMC Information Centre - The EMC Journal (Free in the UK)
Henry Ott, Electromagnetic Compatability Engineering
And quite honestly only a complete novice would run a signal under a switching node unless there was no other alternative.
In the past I have provided many links and references, in this instance I am rather disapointed by the question, having seen the problems caused by noise from switching nodes, so I would reccomend you go learn.
THIS IS REFERENCING MY COMMENT ON SWITCHING NODES NOT CRYSTALS.