#include<iostream>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long LL;
const int maxn = 1e5 + 5, INF = 0x3f3f3f3f;
int p[maxn];
bool v[maxn];
vector<int> path;
int h[maxn], e[maxn * 2], ne[maxn * 2], id[maxn * 2], idx;
int edge;

int find(int x){
    if (p[x] != x){
        p[x] = find(p[x]);
    }
    return p[x];
}

void add(int a, int b, int c){
    e[idx] = b, ne[idx] = h[a], id[idx] = c, h[a] = idx++;
}

void dfs(int u, int ed){
    v[u] = 1;
    if (u == ed){
        path.push_back(edge);
        sort(path.begin(), path.end());
        int sz = path.size();
        for(int i = 0; i < sz; i++){
            printf("%d%c", path[i], i == sz - 1 ? '\n' : ' ');
        }
        return;
    }
    for(int i = h[u]; ~i; i = ne[i]){
        int j = e[i];
        if (!v[j]){
            path.push_back(id[i]);
            dfs(j, ed);
            path.pop_back();
        } 
    }
}

int main(){
    int T;
    cin >> T;
    while(T--){
        int n, m;
        scanf("%d%d", &n, &m);
        idx = 0;
        for(int i = 1; i <= n; i++) p[i] = i, h[i] = -1, v[i] = 0;;
        bool success = 0;
        for(int i = 1; i <= m; i++){
            int a, b;
            scanf("%d%d", &a, &b);
            if (success) continue;
            int pa = find(a), pb = find(b);
            if (pa == pb){
                path.clear();
                edge = i;
                dfs(a, b);
                success = 1;
            }
            else{
                p[pa] = pb;
            }
            add(a, b, i), add(b, a, i);
        }
        if (!success) puts("-1");
    }
}