\begin{table}%t1
\caption{\label{tab:smooth_sources}Details of the sources/SWS spectra used in this study.}
\small%\centerline
 {
  \begin{tabular}{l@\  l l l l@\  l l@\  l}
    \hline
    \hline
&&&&&&& \\[-8pt]
    Source& 
    IRAS name&
    AOT$^a$&
    TDT$^b$& 
    Class.$^c$&
    SP98$^d$&
    Spec. Type$^e$& 
    Remarks
    \\
    \hline
    \multicolumn{8}{c}{S stars from \citet{1994yCat.3168....0S} used in
    this study}\\
    R And      & 00213+3817 & 01(2) & 40201723 & 2.SEc  & SE3 & S3, 5-8, 8e       & 18~$\mu$m feat. weak\\
    S Cas      & 01159+7220 & 01(2) & 41602133 & 3.SEp  & SE3 & S3, 4-5, 8e       & 15~$\mu$m feat., 18~$\mu$m feat. absent, C$_2$H$_2$+HCN abs.\\
    W Aql      & 19126-0708 & 01(2) & 16402335 & 3.SEp  & SE3 & S3, 9-6, 9e       & 15~$\mu$m feat., 18~$\mu$m feat. absent, C$_2$H$_2$+HCN abs.\\
    R Cyg      & 19354+5005 & 01(1) & 42201625 & 2.SEb  & SE3 & S2.5, 9-6, 9e     & 18~$\mu$m feat. absent, 10~$\mu$m feat. narrow\\
    $\chi$ Cyg & 19486+3247 & 01(2) & 15900437 & 2.SEb  & SE3 & S6, 2-10, 4e      & 18~$\mu$m feat. absent, substructure at 10.2~$\mu$m\\
    AA Cyg     & 20026+3640 & 01(2) & 36401817 & 2.M    & N   & S7, 5-7.5, 6      & :            \\              
    RZ Sgr     & 20120-4433 & 01(2) & 14100818 & 2.SEa  & SE2 & S4, 4ep          & \\
    $\pi^1$~Gru& 22196-4612 & 01(2) & 34402039 & 2.SEa  & SE2 & S7, 5e           & 18~$\mu$m feat. absent \\
    RX Lac     & 22476+4047 & 01(1) & 78200427 & 2.SEa  & SE1 & M7.5Se          & :\\
    \hline
    \multicolumn{8}{c}{Stars from \citet{1994yCat.3168....0S} not included in the S star sample}\\
    W Cet      & 23595-1457 & 01(2) & 37802225 & 2.SEa: & --   & S7$^{e1}$       & Low SNR\\                    
    T Cet      & 00192-2020 & 01(2) & 55502308 & 2.SEa  & SE1t& M5-6S IIe       & M supergiant, M, MS or S\\   
    RW And     & 00445+3224 & 01(3) & 42301901 & 7      & SE3:& M5-10e(S6,2e)   & Low SNR\\                     
    WX Cam     & 03452+5301 & 01(2) & 81002721 & 1.NO   & --   & S5/5.5$^{e2}$   & Low SNR\\                     
    NO Aur     & 05374+3153 & 01(1) & 86603434 & 2.SEa  & SE1 & M2S Iab         & Supergiant\\                 
    LY Mus     & 13372-7136 & 01(2) & 13201304 & 1.NO   & --   & M4III$^{e1}$    & No dust features\\            
    II Lup     & 15954-5114 & 06    & 29700401 & 3.CE$^{c1}$&--& SC$^{e3}$       & Carbon-rich\\                
    ST Her     & 15492+4837 & 01(3) & 41901305 & 2.SEa  & SE1 & M6-7 IIIaS      & MS\\                         
    OP Her$^f$ & 17553+4521 & 01(1) & 77800625 & 1.NO   & N   & M5 IIb-IIIa(S)  & No dust features\\           
    HD 165774  & 18058-3658 & 01(2) & 14100603 & 1.NO:  & --   & M2II/III$^{e1}$ & No dust features, low SNR\\  
    S Lyr      & 19111+2555 & 01(1) & 52000546 & 2.CE:  & SE2 & SCe             & Low SNR\\                    
    HR Peg     & 22521+1640 & 01(2) & 37401910 & 1.NO   & --   & S5,1$^{e1}$     & No dust features\\           
    GZ Peg     & 23070+0824 & 01(3) & 37600306 & 1.NO   & N:  & M4S III         & No dust features\\     \hline
    \multicolumn{8}{c}{Supergiants with 10~$\mu$m features resembling the S stars}\\
    KK Per     & 02068+5619 & 01(1) & 45701204 & 2.SEa  & --   & M2 Iab          & 18~$\mu$m feat. weak, UIR\\
    V605 Cas   & 02167+5926 & 01(2) & 61301202 & 2.SEa: & --   & M2 Iab$^{e4}$   & 18~$\mu$m feat. weak, UIR \\
    AD Per     & 02169+5645 & 01(2) & 78800921 & 2.SEap & --   & M2.5 Iab$^{e5}$ & 18~$\mu$m feat. weak, UIR\\
    NO Aur     & 05374+3153 & 01(1) & 86603434 & 2.SEa  & SE1 & M2S Iab         & 18~$\mu$m feat. weak, UIR \\
    V1749 Cyg  & 20193+3527 & 01(2) & 73000622 & 2.SEb  & SE3t& M3 Iab          & UIR\\
    IRC+40 427 & 20296+4028 & 01(3) & 53000406 & 2.SEap:& --   & M0-2 I$^{e6}$   & 18~$\mu$m feat. absent, UIR\\
    CIT 11     & 20377+3901 & 01(1) & 40503119 & 2.SEb  & --   & M3: Iab         & 18~$\mu$m feat. weak\\
    V354 Cep   & 22317+5838 & 01(2) & 41300101 & 2.SEc  & SE6 & M2.7 Iab        & 15~$\mu$m feat., 18~$\mu$m feat. absent\\
    V582 Cas   & 23278+6000 & 01(1) & 38501620 & 2.SEc  & SE5 & M4 I$^{e7}$     & 18~$\mu$m feat. weak, UIR:\\
    \hline
    \multicolumn{8}{c}{Other sources used in this study}\\
    IRC+50 096 & 03229+4721 & 01(2) & 81002351 & 3.CE   & --   & C$^{e2}$        & Carbon-rich, ``30''~$\mu$m feature \\
    R Hya      & 13269-2301 & 01(1) & 08200502 & 2.SEa  & SE2t& M6-9eS(Tc)      & \\
    TY Dra     & 17361+5746 & 01(2) & 74102309 & 2.SEc  & SE8t& M5-8            & \\
    \hline
  \end{tabular}}
\medskip
$^{a}$ Observing mode used \citep[see][]{1996AetA...315L..49D, 1996AetA...315L..38C}. Numbers in brackets correspond to the scanning speed. $^{b}$~TDT number which uniquely identifies each ISO observation. $^c$~Classification of the SWS~spectrum from \citet{2002ApJS..140..389K}, except
$^{c1}$~\citet{2003ApJS..147..379S}. $^d$~IR~classification in the scheme of    \citet{1998ApJS..119..141S}. 
$^e$~Spectral types are from \citet{1998ApJS..119..141S}; except
$^{e1}$ \citet{2001KFNT...17..409K};
$^{e2}$~\citet{2001yCat.3222....0B};
$^{e3}$ \citet{1998yCat.3206....0B};
$^{e4}$ \citet{1970AJ.....75..602H};
$^{e5}$ \citet{1955ApJ...122..434B};
$^{e6}$ \citet{1978AetAS...34..409S} and
$^{e7}$ \citet{1994AAS...185.4515W}.
$^f$~This source is only listed in the first edition of general catalogue of S~stars \citep{1995yCat.3060....0S} and is classed M~star in the second edition.
\end{table}