This library has been originally developed by Jan @halfbyte Krutisch.
Many thanks to the following contributors (in order of contribution)
@zealot128 (Stefan Wienert) contributed a bunch of new fields on invoice and also helped keeping the specs up to date.
@SubandiK (Subandi Khairun) added a more robust handling of tax rates and fixed bugs in the original code.
@RST-J (Jonas Peschla) added support for vertical tax calculation.
@mnin (Martin Wilhelmi) added support for attachments to put PDFs into your XML to put into your PDFs.
@corny (Julian Kornberger) added support for notes among other things.
@ahmedm10 (Ahmed Abdulmajeed) fixed the line item quantities and enabled different tax reasons per tax
@ronald (Mr. Ronald) added support for SEPA extra fields and more fields for buyer reference
@langalex (Alexander Lang) fixed a missing rounding
@valii2334 (Valentin Lazar) added BT-21 and fixed the ommission of discount reason.