# State of the Art in Metal Matrix Composites Research: A Bibliometric Analysis
## 4 Citation Landscapes
### Citation Landscape of Places  
To determine the citation based linkages for MMC research among various countries, the VoS viewer threshold was set at a minimum of five WoS documents and zero citations per nation. Only 63 countries met this criterion out of a total of 97. Table 18 shows the top thirteen countries having the best citations based TLS values. Compared with the collaboration TLS rankings given in Table 8, it may be observed that the People's Republic of China has topped both the lists. The authors of this country have maximum co-authored links (681) in MMC papers as well as the highest number of mutual citations (20,878) in these WoS articles. India, listed as the nation with the third highest co-authored linkages (350), bagged the second spot in international citation linkage rankings (17,501). Conversely, the USA attained the third highest citation linkages (13,112), although it has the second highest co-authored links (537) in its MMC articles. Similarly, nations like Germany, England, France, Japan, Canada and Spain also attained relatively lower citation based TLS ranks as compared to their respective co-authored works based TLS rankings. However, some countries improved their citation rankings over collaboration ranks. These countries included India, Iran and South Korea. Australia maintained the same rank in both listings. The biggest rankings difference is observed in the case of Iran. Iran has the fourth highest mutually cited TLS (5938), whereas it is ranked only ninth in the co-authored MMC research linkages based TLS (145). This analysis shows that Iranian researchers have relatively higher mutual citations with their international colleagues as compared to other top TLS nations; and lesser internationally co-authored publications against the rest of the top linked countries. Table 19 lists the top ten countries having MMC articles' citation based linkages with the Iranian authors. The top three linked nations are India, People's Republic of China and the USA having their mutual MMC citation link strengths with Iran at 1407, 988 and 568, respectively. Figure 21 depicts the citation network graph among the various countries engaged in MMC research, whereas Figure 22 shows the international citation linkages of Iranian authors.  
Figure 20: The citation network graph of organizations.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Rank** & **Country** & **P** & **Citations** & **Links** & **TLS** \\ \hline
1 & Peoples Republic of China & 2475 & 43,374 & 66 & 20,878 \\
2 & India & 2509 & 34,715 & 66 & 17,501 \\
3 & USA & 1104 & 33,038 & 66 & 13,112 \\
4 & Iran & 463 & 10,830 & 63 & 5938 \\
5 & Germany & 525 & 11,654 & 64 & 5042 \\
6 & Turkey & 392 & 7784 & 62 & 4678 \\
7 & England & 325 & 10,849 & 64 & 3799 \\
8 & South Korea & 372 & 6264 & 62 & 3598 \\
9 & Japan & 312 & 6452 & 64 & 3489 \\
10 & France & 282 & 7011 & 61 & 3397 \\
11 & Australia & 172 & 5240 & 64 & 3077 \\
12 & Canada & 259 & 6846 & 59 & 2922 \\
13 & Spain & 245 & 5763 & 61 & 2797 \\ \hline \hline \end{tabular}
\end{table}
Table 19: The top 10 citation links of Iran.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sr. No.** & **Linked Country** & **Link Strength** \\ \hline
1 & India & 1407 \\
2 & Peoples Republic of China & 988 \\
3 & USA & 568 \\
4 & Turkey & 261 \\
5 & South Korea & 184 \\
6 & Australia & 160 \\
7 & Germany & 153 \\
8 & England & 150 \\
9 & Egypt & 145 \\
10 & Japan & 140 \\ \hline \hline \end{tabular}
\end{table}
Table 18: The top 13 countries with the maximum citation TLS values.  
Figure 21: The citation network graph of countries.