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Thanks, that worked perfectly!

Hi, sorry for the brief post, I was in a hurry.
I tried calligra, while it does look close to the font I'm looking for, it's still slightly different. And it doesn't seem to work in formulas - which is what I need it for. The image I posted is from a math publication, and as I'm doing a related work ...

I couldn't find which font to use to get the following letter "B".
Edit: uploaded a larger fragment for context.