These cartoons cannot be used without permission.
Here are the reasons why.
With the increase in image sharing on the internet it's often assumed that web images can automatically be used freely or without permission. This isn't the case. The only images that can be used free or without permission are images where the creator of the image specifically states that this is the case, or where the creator has been dead for a long time (70 years).
Copyright infringement can have serious consequences for practicing artists
The ignoring of copyright is threatening the livelihoods of many people in the creative industries
Correcting a few myths about copyright
It is not true that images can be used without permission if they don't have a copyright symbol - © - on them.
All work is automatically copyright protected by default as soon as it's created. The need for the copyright symbol, ©, or a notice of copyright used to be needed in the USA, but isn't any more
It is not true that images can be used without permission if they are copied from sites that have already used them or have copied them - because the image is then 'in the public domain'.
People sometimes think that because an image is already on a site that the image has therefore been 'sent out into the world'. Maybe they think that it has obviously been paid for already (by the original site for instance), so no other payments are necessary. This is wrong. An image has to be paid for by every user (otherwise, at the very least, the subsequent 'free' users would be taking advantage of the fact that someone else had paid for the work)
It is not true that images can be used without permission if a credit line is added or a link is made to the original site.
The logic behind this fallacy is that the originator of the image is getting useful publicity in lieu of payment, thus everything evens out. That's not quite right unfortunately. The logical conclusion of this justification is that everyone using images can use images for free and the people who create them get nothing but publicity that they may not want or need, thus the image creators starve
Other common justifications for violating copyright - all of them wrong!
Because the originator of the image is getting free publicity
Because no one loses anything by them being used in this way
Because they were originally donated free of charge for a specific use
Because everyone shares things like books by passing them round, and that's okay, so why shouldn't they share images?
Because people should create work for the sheer pleasure of creating it and not for financial reward.