#include <bits/stdc++.h>
using namespace std;

#define ll long long
set <int> st;
vector <int> v[30];
vector < pair <int, int> > topsort;
vector <char> ans;
string s[109];
int visit[30], visit2[30];

void dfs(int val, int cnt)

{
    for(int i = 0; i < v[val].size(); i++) {
        dfs(v[val][i], cnt + 1);
    }

    //visit[val] = max(visit[val], cnt);
    topsort.push_back(make_pair(cnt, val));
}

void dfs2(int val) {

    int cnt = 0;
    for(int i = 0; i < v[val].size(); i++) {
        dfs2(v[val][i]);
    }

    st.insert(val);
}

int main()

{
    ll t;
    cin >> t;
    while(t--) {
        //memset(visit, 0, sizeof(visit));
        memset(visit2, 0, sizeof(visit2));
        ll n;
        scanf("%lld", &n);
        for(int i = 0; i < n; i++)
            cin >> s[i];

        for(int i = 0; i < n - 1; i++) {

            ll len = min(s[i].length(), s[i + 1].length());
            for(int j = 0; j < len; j++) {
                if(s[i][j] == s[i + 1][j])
                    continue;
                else {

                    v[ s[i][j] - 'a' ].push_back(s[i + 1][j] - 'a');
                    break;
                }
            }
        }

        int cnt = 0, start;
        for(int i = 0; i <= 26; i++) {
            if(v[i].size() == 0)
                continue;
            dfs2(i);
            int tmp = st.size();
            if(cnt < tmp ) {
                cnt = tmp;
                start = i;
            }
            st.clear();
        }

        dfs(start, 1);
        sort(topsort.begin(), topsort.end());
        for(int i = topsort.size() - 1; i >= 0; i--) {
            if( visit2[topsort[i].second])
                continue;

            visit2[topsort[i].second] = 1;
            ans.push_back(topsort[i].second + 'a');
        }

        for(int i = ans.size() - 1; i >= 0; i--) {
            printf("%c", ans[i]);
            if(i != 0)
                printf(" ");
            else
                printf("\n");
        }

        for(int i = 0; i <= 28; i++) {
            v[i].clear();
        }

        topsort.clear();
        ans.clear();
    }

    return 0;
}