Grazie OldClaudio. Ho modificato il codice (preambolo) come suggerito (in realtà mi mancava solo \newcolumntype).
In realtà sembra che non funzioni perfettamente, pertanto allego risultato in .pdf e mio preambolo.
\documentclass[]{dukedissertation}
%\documentclass[economy,twoside,bind]{dukedissertation}
% Use the second for a single-spaced copy suitable for duplex printing
% and binding.
% Other useful options (there are more options documented in Chapter 2):
% * draft — don’t actually include images, print a black bar on overful
% hboxes
% * MS — Format for a Master’s Thesis. No UMI abstract page, some
% textual changes to title page.
% Useful packages for dissertation writing:
\usepackage{amsmath, amssymb, amsfonts, amsthm}
\usepackage{graphicx}
\usepackage{natbib}
\usepackage{color}
\usepackage{bm}
\usepackage{subfigure}
\usepackage{mathabx}
\usepackage{multirow}
\usepackage{setspace}
% pacchetto array aggiunto da Andrea
\usepackage{array}
% pacchetto rotating aggiunto da Andrea
\usepackage{rotating}
% pacchetto booktabs aggiunto da Andrea
\usepackage{booktabs}
%pacchetto caption aggiunto da Andrea
\usepackage{caption}
\captionsetup{tableposition=top, figureposition=bottom, font=small}
% pacchetto bmpsize aggiunto da Andrea
\usepackage{bmpsize}
% pacchetto indentfirst aggiunto da Andrea
\usepackage{indentfirst}
% pacchetto microtype aggiunto da Andrea
\usepackage{microtype}
% pacchetto quoting aggiunto da Andrea
\usepackage{quoting}
\quotingsetup{font=small}
% pacchetto siunitx aggiunto da Andrea
\usepackage{siunitx}
% pacchetto tabularx aggiunto da Andrea
\usepackage{tabularx}
% \usepackage{cite} % If you include this, hyperlink cites will
% break. It’s nice to use this package if your bibstyle
% sorts entries by order-of-use, rather than
% alphabetically (as plain does).
%Theorem, Lemma, etc. environments
\newtheorem{theorem}{Theorem}%[section]
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{proposition}[theorem]{Proposition}
\newtheorem{corollary}[theorem]{Corollary}
\newtheorem{result}[theorem]{Result}
% Personal commands and abbreviations.
%Define and personal commands here
%\newcommand{\api}{\textsuperscript{}}
\newcolumntype{P}[1]{>{\centering}p{#1}}
%Graphics Path to find your pictures
\graphicspath{{./Pictures/}}
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Dove sarà l’errore?
Grazie ancora
°-Arekhnames-°
[attachment=449]tabella1.pdf[/attachment]