`\documentclass[10pt,a4paper,openright,titlepage,fleqn,%oneside,%
cleardoublepage=empty,numbers=noenddot,headinclude,twoside,%
BCOR10mm,captions=tableheading]
{scrbook}
% PACCHETTI CARICATI
\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[italian,english]{babel}
\usepackage{amsmath,amssymb,amsfonts,amsthm}
% definizione dello stile
\usepackage{classicthesis-ldpkg}
\usepackage[eulerchapternumbers,subfig,beramono,pdfspacing]{classicthesis}
\usepackage[italian]{arsclassica}
% Personalizzazione comandi
\DeclareMathOperator{\D}{D} % Simbolo di derivata con D
\newcommand{\Df}[3]{\mathop{^{}_{#2}\mkern-1mu\D_{#3}^{#1}\!}}
% Documento
\begin{document}
\selectlanguage{italian}
\mainmatter
\chapter{capitolo di esempio}
\begin{equation}
\Df{\alpha}{a}{t}
\end{equation}
\end{document}
`
Spero sia sufficientemente minimo…