BibLaTeX: Modern Citations in LaTeX

\documentclass{article}
\usepackage[backend=biber, style=authoryear]{biblatex}
\addbibresource{references.bib}  % Your .bib file

\begin{document}

\section{Introduction}
According to \textcite{einstein1905}, the theory states...

This is supported by recent research \parencite{hawking1988}.

\printbibliography

\end{document}

# Standard compilation sequence
pdflatex document.tex
biber document        # Run Biber (not bibtex!)
pdflatex document.tex
pdflatex document.tex

# Or use latexmk for automatic compilation
latexmk -pdf -pdflatex="pdflatex -interaction=nonstopmode" document.tex

% Basic options
\usepackage[
  backend=biber,           % Use Biber backend
  style=authoryear,        % Citation style
  sorting=nyt,             % Sort by name, year, title
  maxbibnames=99,          % Show all authors
  maxcitenames=2,          % Max 2 authors in citations
  giveninits=true,         % Use initials for first names
  uniquename=init,         % Disambiguate with initials
  uniquelist=true,         % Unique author lists
  doi=true,                % Print DOIs
  isbn=false,              % Don't print ISBNs
  url=true,                % Print URLs
  eprint=false             % Don't print arXiv IDs
]{biblatex}

% For numeric citations
\usepackage[backend=biber, style=numeric, sorting=none]{biblatex}

% For alphabetic citations
\usepackage[backend=biber, style=alphabetic]{biblatex}

% In-text citations
\textcite{key}           % Einstein (1905)
\textcites{key1}{key2}   % Einstein (1905) and Bohr (1913)

% Parenthetical citations
\parencite{key}          % (Einstein, 1905)
\parencite[see][p. 5]{key}  % (see Einstein, 1905, p. 5)

% Author only
\citeauthor{key}         % Einstein

% Year only
\citeyear{key}           % 1905

% Title
\citetitle{key}          % On the Electrodynamics...

% Full citation in text
\fullcite{key}           % Einstein, A. (1905). On the...

% Footnote citation
\footcite{key}           % Adds citation in footnote

% Multiple citations in one command
\parencite{einstein1905, bohr1913, heisenberg1927}
% Output: (Einstein, 1905; Bohr, 1913; Heisenberg, 1927)

% With individual pre/post notes
\parencites[see][]{einstein1905}[cf.][p. 10]{bohr1913}
% Output: (see Einstein, 1905; cf. Bohr, 1913, p. 10)

% Suppress author
\parencite*{key}         % (1905) - author suppressed
\textcite*{key}          % Einstein 1905 - no parentheses

% Basic bibliography
\printbibliography

% With custom title
\printbibliography[title={References}]

% Filter by entry type
\printbibliography[type=article, title={Journal Articles}]
\printbibliography[type=book, title={Books}]

% Filter by keyword
\printbibliography[keyword=primary, title={Primary Sources}]
\printbibliography[notkeyword=primary, title={Secondary Sources}]

% Not cited entries (all entries in .bib file)
\nocite{*}  % Include all entries
\printbibliography

% Numeric with compact formatting
\usepackage[style=numeric-comp]{biblatex}

% Authoryear with verbose citations
\usepackage[style=authoryear-icomp]{biblatex}

% Alphabetic verbose
\usepackage[style=alphabetic-verb]{biblatex}

% IEEE style
\usepackage[style=ieee]{biblatex}

% APA style (requires biblatex-apa package)
\usepackage[style=apa]{biblatex}

% Chicago style (requires biblatex-chicago package)
\usepackage[style=chicago-authordate]{biblatex}

% Install via package manager
tlmgr install biblatex-apa      % APA 7th edition
tlmgr install biblatex-chicago  % Chicago Manual of Style
tlmgr install biblatex-ieee     % IEEE style
tlmgr install biblatex-mla      % MLA style
tlmgr install biblatex-nature   % Nature journal style

% Use in document
\usepackage[style=apa]{biblatex}
\usepackage[style=chicago-authordate]{biblatex}
\usepackage[style=ieee]{biblatex}

% Postnote (after citation)
\parencite[p. 25]{key}           % (Einstein, 1905, p. 25)
\parencite[pp. 25-30]{key}       % (Einstein, 1905, pp. 25-30)
\parencite[Chapter 3]{key}       % (Einstein, 1905, Chapter 3)

% Prenote and postnote
\parencite[see][p. 25]{key}      % (see Einstein, 1905, p. 25)
\parencite[cf.][]{key}           % (cf. Einstein, 1905)

% Empty postnote to add prenote only
\textcite[see][]{key}            % see Einstein (1905)

% Automatic capitalization
\Textcite{key}    % Einstein (1905) - capital E
\Parencite{key}   % (Einstein, 1905)

% Automatic punctuation
\autocite{key}    % Adapts to context
% In footnote style: adds footnote
% In author-year: uses \parencite
% In numeric: uses \cite

% Smart cite (adds punctuation tracker)
As shown by \smartcite{key}, the theory...
% Properly handles: As shown by (Einstein, 1905), the...

% In .bib file
@incollection{chapter1,
  author = {Smith, John},
  title = {Introduction},
  crossref = {book1}
}

@book{book1,
  editor = {Doe, Jane},
  title = {Collection of Papers},
  year = {2020},
  publisher = {Academic Press}
}

% Automatically inherits book information
\cite{chapter1}
% Output: Smith (2020, in Doe 2020)

% Define custom citation style
\DeclareCiteCommand{\customcite}
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \printnames{labelname} (\printfield{year})}
  {\multicitedelim}
  {\usebibmacro{postnote}}

% Use it
\customcite{key}  % Uses your custom format

% Shorthand citation
\newcommand{\scite}[1]{\parencite[see][]{#1}}
\scite{key}  % (see Einstein, 1905)

% Name formatting
\DeclareNameAlias{author}{family-given}  % Lastname, Firstname
\DeclareNameAlias{author}{given-family}  % Firstname Lastname

% Title formatting
\DeclareFieldFormat[article]{title}{#1}  % No quotes
\DeclareFieldFormat[book]{title}{\mkbibemph{#1}}  % Italic

% URL formatting
\DeclareFieldFormat{url}{\url{#1}}
\DeclareFieldFormat{doi}{DOI: \url{https://doi.org/#1}}

% Date format
\DefineBibliographyStrings{english}{
  january = {Jan.},
  february = {Feb.},
  % ... abbreviate months
}

% Punctuation
\renewcommand{\newunitpunct}{\addcomma\space}  % Use commas
\renewcommand{\finentrypunct}{}  % No period at end

% Load with sorting option
\usepackage[sorting=nyt]{biblatex}  % name, year, title
\usepackage[sorting=nty]{biblatex}  % name, title, year
\usepackage[sorting=ynt]{biblatex}  % year, name, title
\usepackage[sorting=none]{biblatex} % citation order
\usepackage[sorting=debug]{biblatex} % entry order (debug)

% Custom sort scheme
\DeclareSortingScheme{custom}{
  \sort{\field{author}}
  \sort{\field{year}}
  \sort{\field{title}}
}

\usepackage[sorting=custom]{biblatex}

% Load babel for language support
\usepackage[english, french, german]{babel}
\usepackage[autolang=other]{biblatex}

% Entries switch language automatically
@book{german-book,
  author = {Müller, Hans},
  title = {Deutsche Titel},
  language = {german},
  year = {2020}
}

% Custom strings per language
\DefineBibliographyStrings{german}{
  andothers = {et al.},
  references = {Literaturverzeichnis}
}

@article{einstein1905,
  author = {Einstein, Albert},
  title = {On the Electrodynamics of Moving Bodies},
  journal = {Annalen der Physik},
  year = {1905},
  volume = {17},
  number = {10},
  pages = {891--921},
  doi = {10.1002/andp.19053221004},
  language = {english},
  keywords = {relativity, physics}
}

@book{hawking1988,
  author = {Hawking, Stephen W.},
  title = {A Brief History of Time},
  subtitle = {From the Big Bang to Black Holes},
  year = {1988},
  publisher = {Bantam Books},
  location = {New York},
  isbn = {0-553-38016-8},
  keywords = {cosmology}
}

@online{wiki2024,
  author = {{Wikipedia contributors}},
  title = {Quantum Mechanics},
  year = {2024},
  url = {https://en.wikipedia.org/wiki/Quantum_mechanics},
  urldate = {2024-01-15},
  organization = {Wikipedia, The Free Encyclopedia}
}

@article{advanced,
  author = {Smith, John and Doe, Jane},
  title = {Advanced Research},
  journal = {Journal Name},
  year = {2024},
  
  % Additional identifiers
  doi = {10.1234/example},
  eprint = {2401.12345},        % arXiv ID
  eprinttype = {arxiv},
  
  % Additional information
  annotation = {Important paper on topic X},
  abstract = {This paper discusses...},
  keywords = {primary, experimental},
  
  % Version and revision
  version = {2},
  
  % URLs and dates
  url = {https://example.com/paper.pdf},
  urldate = {2024-01-15}
}

\documentclass{article}
\usepackage[defernumbers=true]{biblatex}
\addbibresource{references.bib}

\begin{document}

\section{Content}
Some citations here...

% Print separate bibliographies
\printbibliography[type=book, title={Books}]
\printbibliography[type=article, title={Journal Articles}]
\printbibliography[type=online, title={Online Sources}]

\end{document}

% Define categories
\DeclareBibliographyCategory{primary}
\DeclareBibliographyCategory{secondary}

% Assign entries to categories
\addtocategory{primary}{einstein1905, bohr1913}
\addtocategory{secondary}{hawking1988}

% Print by category
\printbibliography[category=primary, title={Primary Sources}]
\printbibliography[category=secondary, title={Secondary Sources}]

\documentclass{book}
\usepackage[refsection=chapter]{biblatex}
\addbibresource{references.bib}

\begin{document}

\chapter{First Chapter}
\begin{refsection}
  Content and citations...
  \printbibliography[heading=subbibliography]
\end{refsection}

\chapter{Second Chapter}
\begin{refsection}
  More content and citations...
  \printbibliography[heading=subbibliography]
\end{refsection}

\end{document}

% OLD BibTeX way
\documentclass{article}
\begin{document}
According to \cite{key}, ...
\bibliographystyle{plain}
\bibliography{references}
\end{document}

% NEW BibLaTeX way
\documentclass{article}
\usepackage[style=numeric]{biblatex}
\addbibresource{references.bib}  % Add .bib extension!
\begin{document}
According to \parencite{key}, ...
\printbibliography
\end{document}

% Check these common issues:
1. Did you run biber (not bibtex)?
   Command: biber filename (without .tex)

2. Is the .bib file in the correct location?
   \addbibresource{references.bib}  % Same directory
   \addbibresource{../refs/references.bib}  % Relative path

3. Did you cite something?
   % Add \nocite{*} to show all entries
   
4. Full compilation sequence:
   pdflatex → biber → pdflatex → pdflatex

% If you see [?] in output:
1. Check citation key spelling in \cite{key}
2. Verify entry exists in .bib file
3. Run full compilation cycle
4. Check biber output for errors:
   biber --debug filename

% Biber version mismatch
% Delete cache and recompile:
rm -rf `biber --cache`  # Unix/Mac
biber --cache           # Windows: manually delete folder

% Force rerun
biber --validate-datamodel filename