LaTeX.org

Unless you're using another class called `ecv' than available through CTAN, the class already uses helvet and switches to sans serif at document start. So for `helvet', you don't need to change anything. For using `times', you'd need to not only load the package, but issue \normalfont just after \be...

\left as well as \right require an argument, typically one off \{[(. for \left and one off .)]\} for \right.
If you don't need delimiters to be expanded on either side, omit \left and \right.
If that does not help you, please provide a minimal working example that demonstrates your problem.

KR
Rainer

As I tried to explain earlier https://latex.org/forum/viewtopic.php?f=19&t=33812, \sen is defined by babel in Spanish context.
Try this

Hi there,
since there's no entry for `journal2' on CTAN, what makes you think it should work?

KR
Rainer

! Undefined control sequence. \sin ->\sen \nolimits l.751 ... \textbf{momento} es$\:$ $mlH_{1}=mlH\sin \alphaup$ \sen is defined by babel's Spanish language definition file (spanish.ldf), so you're either using a different language (where \sen is void), something went wrong with loading spanish.ldf...

weird.
Try

to switch to your style and

to switch back to the original page style.

Or if your style is limited to a single page anyway, try

instead.

KR
Rainer

I'm not sure why you tagged this thread as `solved' (isn't that what the green tick is all about?) Anyway, I'd omit the twocolumn option to the class: you want to start with onecolumn... If you switch to twocolumn just after your frontmatter, you'd get the frontmatter stuff on the first page (in one...

and how did you create this new page style of yours?

KR
Rainer

Could you please provide a minimal working example?
When I expand your snippets to one, I don't see what you see...

kallsbo wrote:The title is also missing the -

There's no `-' in the title of your posted bib entry, either.
Or which `-' do you mean?

KR
Rainer

That should be possible with the totcount package.

KR
Rainer