I'm not used to Einstein notation and I'm struggling a bit with the more complex examples of it. I got the general gist of it and can follow the basic cases but get sometimes a bit lost when there are a lot of indexes and calculus is involved. All primers I've found online for now only give the basic rules - sum over repeated indices, Kronecker delta, Levi-Civita symbol, and that's it. Is there some good 'reference sheet' I could use to look up more sophisticated cases like those involving derivation rules? I realise they can easily be derived from considering the represented sum, and in some cases I manage to do that, but the convenience of the notation should be to avoid having to write sums explicitly all the time, and knowing the rule beforehand I could at least work out why and how it applies and then trust it going forward. Thanks!