Is it proper to use firstly..., secondly ..., thirdly ... in academic writings?

[lrc007]

One of my friend in Canada suggests that the -ly suffix attached to the numerical is unidiomatic in English. Is that true? Should we only use first, second, third in formal context?

 

[Offroad]

[I am not a teacher]

I've edited, written and read many papers during my career as an engineer and I can assure you I have never seen any of these. I would not use them.

 

[lrc007]

Thanks for your help!