Fuzzy logic operator symbols

Question

How can I write in Latex symbols for standard or Łukasiewicz conjunction like these?

Thank you

Answer 1

This keeps the "S" and "L" in non-italic upshape, as given in your example.

\documentclass{article}
\usepackage{stackengine}
\begin{document} 
$ a \mathrel{\stackunder[-1pt]{$\wedge$}{\tiny L}} 
  b \mathrel{\stackunder[-1pt]{$\wedge$}{\tiny S}} c$
\end{document}

Answer 2

If you don't need them in subscripts or superscripts, here's a way:

\documentclass{article}

\newcommand{\landl}{\mathbin{\landx{L}}}
\newcommand{\lands}{\mathbin{\landx{S}}}

\newcommand{\landx}[1]{%
  \ooalign{%
    $\land$\cr
    \noalign{\kern.5ex}
    \hidewidth$\scriptscriptstyle#1\mkern1.5mu$\hidewidth\cr
  }%
}

\begin{document}
$a\landl b\lands c$
\end{document}